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					                    “Satisfaction Through
                      Superior Service”




          Metropolitan Washington Region
              Traffic Signal Systems
                    White Paper
                                  FINAL DRAFT

                              Prepared for:
             Metropolitan Washington Council of Governments

                                  May 29, 2002




Trichord, Inc.                                   Quality Consultants Group
12888 James Monroe Highway                       303 East Glendale Avenue
Leesburg, VA 20176                               Suite 2
(703) 737-0162                                   Alexandria, VA 22301
www.trichord-inc.com
   METROPOLITAN WASHINGTON REGION TRAFFIC SIGNAL SYSTEMS
                       WHITE PAPER

                                                                           Final Draft

                                                                         May 29, 2002

EXECUTIVE SUMMARY
1.0          INTRODUCTION ......................................................................................................................................... 1
    1.1          BACKGROUND .................................................................................................................. 1
    1.2          PURPOSE .......................................................................................................................... 1
2.0          TRAFFIC SIGNAL OPERATIONS AND MAINTENANCE IN THE METROPOLITAN
             WASHINGTON REGION ........................................................................................................................... 2
    2.1          TRAFFIC SIGNAL OPERATIONS ......................................................................................... 2
    2.2          TRAFFIC SIGNAL MAINTENANCE ..................................................................................... 6
    2.3          SURVEY RESULTS: JURISDICTIONAL SIGNAL SYSTEMS PROGRAMS................................. 7
    2.4          AGENCY COMMENTS ON SIGNAL SYSTEMS OPERATIONS .............................................. 17
    2.5          AGENCY COMMENTS ON SIGNAL MAINTENANCE PROGRAMS ....................................... 17
3.0          OPPORTUNITIES FOR COLLABORATION/ IMPROVEMENT PLANS......................................... 19

4.0          CONCLUSIONS.......................................................................................................................................... 22

APPENDIX A: NARRATIVE SUMMARY OF AGENCY SURVEY RESULTS .............................................. 24

GLOSSARY ............................................................................................................................................................... 34




Traffic Signal Operations White Paper                                                                                                                Trichord, Inc.
                                                                                                                                         Quality Consultants Group
EXECUTIVE SUMMARY

Severe traffic demands are being placed on the major arterials in the Metropolitan Washington
region — no longer just during the typical weekday rush hour periods. Rather, these demands
are occurring more frequently throughout the day, virtually every day. Many of these demands
involve conflicting vehicular and pedestrian movements that require a high degree of traffic
control to assign rights-of-way.

When incorporated into a system that operates interdependently, traffic signals are one of the
best tools for state and local traffic engineers to use in addressing these traffic demands and
conflicts — not only on corridors within particular jurisdictional boundaries, but throughout the
Metropolitan Washington region.

Traffic engineers and transportation professionals in the Metropolitan Washington region face a
number of technical challenges and resource conflicts in their quest to optimize traffic flow and
signal coordination. At a technical level, traffic engineers address issues in signal coordination,
communications, and traffic control strategies. At a financial resources and staffing level, traffic
engineers address management, operations, and maintenance issues.

This traffic signal systems white paper summarizes the region’s capabilities in traffic control,
signal operations, and system maintenance. It presents the results of a regional survey of signal
system capabilities, categorizes the signal system capabilities, and identifies system
characteristics by geographic area.

Throughout the Metropolitan Washington region, significant coordination of traffic signals
occurs both within individual jurisdictions and between regional partners. There are currently
several ongoing multi-jurisdictional traffic signal activities that promote regional objectives to
improve traffic flow and safety in the region. These efforts, facilitated by the Metropolitan
Washington Council of Governments (MWCOG), include the Pilot Arterial Corridor project, the
regional traffic signal problem reporting system website, and the Traffic Signal
Preemption/Priority study. From these activities, many regional partners have discovered
unexpected similarities in their signal systems.

Each jurisdiction is trying to optimize the use of technology to save money. Integrated Traffic
Management Systems (ITMS) is the next technological phase for many transportation agencies
around the country — the Metropolitan Washington region is part of this evolution. The District
of Columbia Department of Public Works currently has an ITMS initiative underway, which will
integrate their arterial and freeway management operations (as well as some emergency services
functions) into one center. It is envisioned that this effort will serve as a springboard for other
agencies to begin considering the ―hard‖ integration of functions and technologies to better serve
their own needs, as well as the needs of the region.

Likely candidates for future potential opportunities involve those agencies that have both signal
systems and freeway management system operations, e.g., CHART and Montgomery County’s
ATMS, as well as VDOT’s Northern Virginia District Smart Traffic Center and its Traffic Signal
System.


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All of the transportation agencies throughout the Metropolitan Washington region are taking
tremendous advantage of the evolution of computer technology and using it to more efficiently
and effectively operate and maintain their traffic signals and systems. Common areas of
technology include the prevalent use of NEMA controllers and SYNCHRO optimization
software, as well as system data archiving activities.

The region is performing well under difficult circumstances. In the face of limited staffing and
funding, transportation agencies’ staff continue to find creative ways to use technology to help
save time and money, as well as to maximize their limited dollars and staff - especially in the
area of signal maintenance.

The region could perform better with additional resources. While all agencies are doing a great
job with what they have, these transportation officials could do even more, if additional
resources were made available, including:

   More staff, in order to be more proactive and responsive in systems operations and
    maintenance (for example, increased staffing levels would enable the agency to perform
    signal retiming and optimization on a routine basis, to keep up with the real world
    fluctuations of traffic demand and citizens’ complaints)
   Closed circuit television for remote system monitoring (to include verification and resolution
    of traffic and system problems before going out into the field; e.g. immediate adjusting of
    signal timings during an incident or identification of a signal bulb outage)
   Video detection
   Access to more communications infrastructure with greater bandwidth capabilities
   Greater event tracking capabilities within the systems (created in a database format to enable
    query of activities)
   Ability to observe signal operations in an off-line format
   Communication between the on-street master controllers
   Expanded master controller capabilities and functions
   Better traffic signal coordination capabilities, specifically on side streets
   Improvement of traffic responsive features to make procedures less cumbersome
   Ability to review preemption information from a central location
   Capability to work directly with optimization software from the system.

While facing the everyday reality of limited staffing and funding resources, these agencies still
manage to take a proactive approach to traffic management by utilizing a variety of tools to
mitigate the effects of increasing vehicular, bicycle, and pedestrian demands on the limited
capacity of transportation facilities in the region.



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Although the functional responsibilities and the technical complexity and size of each agency’s
systems vary, there is no doubt that each jurisdiction’s system functionality is very important
plays a vital role in meeting the transportation goals of the regional transportation network.
These transportation agencies are operating and maintaining their systems to meet a
demonstrated need locally, while at the same time, also providing a valuable service and benefit
to the region.




Traffic Signal Operations White Paper      iii                                           Trichord, Inc.
                                                                             Quality Consultants Group
1.0      INTRODUCTION

Severe traffic demands are being placed on the major arterials in the Metropolitan Washington
region — no longer just during the typical weekday rush hour periods. Rather, these demands
are occurring more frequently throughout the day, virtually every day, and many of these
demands involve conflicting vehicular and pedestrian movements that require a high degree of
traffic control to assign rights-of-way.

While there are various schools of thought on the need for traffic signals (and their advantages
and disadvantages when installed), it has been shown that when a traffic signal is appropriately
justified, properly designed, and effectively operated and maintained, it can be one of the best
tools for state and local traffic engineers to use to address these traffic demands and conflicts.

When incorporated into a system that operates interdependently, traffic signals can be one of a
jurisdiction’s most effective tools to assist in keeping traffic flowing in an efficient and safe
manner — not only on corridors within its own jurisdictional boundaries, but throughout a
region.

1.1    Background

In the 2000 The Region report (Vol. 39) published by the Metropolitan Washington Council of
Governments, one of the main elements in Theme # 3 of the ―Key Themes of the Vision‖ for the
region is ―the need to put together a package of projects to fund.‖ Within this element, projects
were categorized into three (3) basic types: Fix-up, Enhancement, and Expansion.

In the ―Fix-up‖ category, the report stated that ―the region needs to invest more for fix-ups, such
as sidewalk and traffic signal maintenance‖; under the ―Enhancement‖ category, the Council of
Governments felt that investments in strategic improvements in areas such as traffic control
would help the region get a lot more out of its existing transportation system. The
implementation, operation, and maintenance of computerized traffic signals and systems is an
example of one such strategic improvement being effectively used in the Metropolitan
Washington region.

Because of the numerous jurisdictions in the Washington metropolitan region and the ―invisible‖
jurisdictional boundaries that the traveling public experiences on these major highway corridors,
it is critical that a high level of communication, coordination, and cooperation take place among
responsible transportation agencies in traffic matters. In the Metropolitan Washington region,
experience has shown that state and local transportation officials have taken a strong and visible
leadership role to ensure that this takes place.

1.2    Purpose

The purpose of this paper is to document not only the technical aspects of the traffic signal
system programs being operated and maintained around the Metropolitan Washington region, but
also to highlight the creativity and successes of state and local transportation agencies in
addressing the challenges and opportunities created by ever increasing traffic demands on limited
capacity facilities — especially in the face of limited staffing and funding.

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2.0      TRAFFIC SIGNAL OPERATIONS AND MAINTENANCE IN THE
         METROPOLITAN WASHINGTON REGION

Traffic signals in the Washington, D.C. region are either a state or local matter – i.e., state and
local transportation agencies are responsible for the justification, administration, installation,
operations, and maintenance of traffic signals in their respective jurisdictional areas. These
individual jurisdictions determine where, when, and how these signals are installed.

Once these signals are installed, however, officials do not just walk away from the devices and
let them work on their own. The operations and maintenance of traffic signals are dynamic, day-
to-day traffic management functions of state and local agencies, performed not only during rush
hour periods, but also during incidents (vehicular and non-vehicular) and special events.

Many signals in the region operate without any relation to an adjacent jurisdiction’s signal
operation. However, as land use development continues to increase and to expand along major
regional corridors (usually resulting in the need for more signals), the likelihood of signals
needing to work interdependently also increases.

2.1     Traffic Signal Operations

When operating a traffic signal system, the traffic engineer must consider a number of technical
issues: signal coordination, communication methods, and control systems.

Signal Coordination: When a corridor has several signals in close proximity, the traffic
engineer may find it beneficial to consider coordinating these signals to improve traffic flow.
Several factors must be reviewed when considering coordination, including (but not limited to):

     Traffic signal spacing
     Traffic volumes (vehicular and pedestrian)
     Turning movements
     Transit activity (loading and off-loading)
     Safety history
     On-street parking
     Traffic speed
     Land use

While the above factors are of a physical, measurable nature, the traffic engineer must also take
into consideration those factors that may be somewhat more difficult to measure, such as driver
comfort and satisfaction. The expectation of the typical ―layperson‖ driver is to experience as
smooth a ride as possible along a corridor, with minimal to no delay or random stops.

Figure 1 identifies which organization is responsible for signal coordination in different parts of
the Metropolitan Washington Region.



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                                    Frederick
                                     County
                                               City of                                         Virginia Department of Transportation
                                              Frederick

                                                                                               Maryland State Highway Administration

                                                                                               DC Department of Public Works
                                                 Montgomery
                                                   County
                                                                                               Montgomery County

                                                                      Rockville                Local Jurisdictions
                 Loudoun
                  County
                              Leesburg

                                  Herndon
                                                          Arlington
                                                           County
                                               Vienna                    Washington,
                                                            Falls           DC
                                    Fairfax                Church
                       Manassas
                         Park                                   Alexandria
                                                   Fairfax                    Prince Georges
                                                   County                         County
                                  Manassas

                                  Prince William
                                      County




              Figure 1: Organizations Responsible for
                        Signal Coordination in the Metropolitan Washington Region


Communications/Interconnection Methods: Once the decision to coordinate has been made,
there are two basic methods that traffic engineers can consider to achieve interconnection:
through a wire-line or a wireless communications connection.

Wire-line Connection. This method uses a physical wire connection to provide two-way
communications between the controller assemblies in the field and/or back to a central control
center. This direct connection can be achieved through various means — the most commonly
used for signal communications in the Metropolitan Washington region being copper wire,
coaxial cable, fiber optic cable, and leased lines.

Copper wire, also referred to as twisted pairs, is a widely used medium for interconnection of
traffic signals. The copper cables are twisted in pairs in order to reduce electrical interference, or
―cross-talk‖ – interference due to signal ingress in one communication channel caused by signal
egress from an adjacent channel. This medium is mainly used for signal data transfer and has
limited capacity for use with video.

Coaxial cable, initially used mainly by cable television service providers, has been found to have
tremendous benefits to the transportation sector. Coaxial cable, also called ―coax,‖ is a
broadband communications technology that consists of a single inner conductor that has a



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common axis with a second outer conductor (shield). This medium has the capacity of carrying
many channels to transmit data, as well as video.

Fiber Optic cable is rapidly increasing in use by transportation agencies, due to its tremendous
bandwidth capacity (compared to copper and coaxial cable). It is considered analogous to a
multi-coaxial cable, but is much smaller physically, has much greater capacity, can carry a signal
over long distances, and is virtually immune to electromagnetic interference, because it transmits
light pulses (rather than an electrical signal).

Leased Lines are generally telephone-type twisted pairs or fiber optic cables that are leased by
transportation agencies from a local communications company. A major drawback to using
leased lines is the high on-going lease costs that are sometimes tied to the service provider’s
general service rate increases.

Wireless Connection. While not commonly done with traffic signals, transportation agencies
may also utilize wireless connections, such as radio or time-based coordination to achieve
interconnection.

Radio systems are a form of wireless communication connection and come in various forms,
including cellular networks, satellite, and spread spectrum radio. While still not widely used for
traffic signal operations, there are special circumstances where radio may be the best
communications media to utilize. Examples of such circumstances include situations where
there are no available landlines or when right of way is not available for communications
infrastructure installation. There are disadvantages to radio, however, including line of sight
requirements, fading issues, and limited bandwidth capacity.

Time-based coordinators are also used to achieve communications between signals without
cables. These time-based coordinators are basically accurate internal clocks that supervise a
local controller unit by sync pulses and commands, similar to a master controller.
Interconnection is achieved when several adjacent controllers are similarly equipped and operate
from the same time reference point. The obvious drawback to this method is that two-way
communication between controllers cannot be achieved, and the need for the clocks to be
updated on a routine basis to ensure accuracy.

Figure 2 identifies the communication methods used for traffic signal systems in different parts
of the Metropolitan Washington Region.




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                                    Frederick
                                     County

                                                City of
                                               Frederick
                                                                                                Agency-owned Copper Wire

                                                                                                Combination of Agency-owned
                                                  Montgomery                                    Copper and Fiber
                                                    County
                                                                                                Leased Lines
                                                                       Rockville
                  Loudoun                                                                       Agency-owned Copper Wire,
                   County
                                  Leesburg                                                      Fiber, and Leased Lines
                                  Herndon
                                                           Arlington                            Leased Fiber
                                                            County
                                                Vienna                    Washington,
                                                             Falls           DC                 Combination of Owned Copper
                                     Fairfax                Church
                                                                                                & Leased Lines
                       Manassas
                         Park                                    Alexandria
                                                    Fairfax
                                                                               Prince Georges
                                                    County                                      Information Unavailable
                                                                                   County
                                  Manassas

                             Prince William
                                 County




              Figure 2: Communication Methods


Control Systems: There are several control systems available for signal system operation.
Three types of control systems in operation in the Metropolitan Washington region include:
(1) central control systems, (2) closed loop systems, and (3) hybrid systems.

1. Central control systems involve a computer control system in which the master computer,
   central communication facilities, console, keyboard, and display equipment are all situated at
   one location (e.g. a signal operations center). This approach can include the use of a master
   controller to control cycle lengths, offset and split for each cycle; or, a mutually coordinated
   system of intersections that does not require a master controller. Signal system staff
   coordinate and control traffic signals throughout a defined geographic area from the signal
   operations center.
2. Closed loop systems provide two-way field communication between the intersection signal
   controller and its master controller. The master controller then communicates information
   back to the signal operations center.
3. Hybrid systems are a combination of various control systems, strategies and technologies
   that a jurisdiction implements in a systematic fashion (e.g., time-based coordination, isolated
   intersections, etc.).




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These computerized signal systems, with their communications links, provide great operations
and maintenance benefits to transportation agencies’ staff. Personnel can use these systems to
(remotely) monitor and adjust signals, as well as to respond more efficiently to incidents (e.g.,
adjusting signal timing in real-time during incidents and special events).

Figure 3 identifies the types of control systems used in different parts of the Metropolitan
Washington Region.




                                               Frederick
                                                County

                                                          City of
                                                         Frederick


                                                                                                           Central

                                                            Montgomery                                     Closed Loop
                                                              County
                                                                                                           Hybrid
                                                                                  Rockville
                             Loudoun
                              County
                                                                                                           Unknown
                                         Leesburg

                                             Herndon
                                                                     Arlington
                                                                      County
                                                          Vienna                     Washington,
                                                                       Falls            DC
                                               Fairfax                Church
                                  Manassas
                                    Park                                     Alexandria
                                                              Fairfax                     Prince Georges
                                                              County                          County
                                             Manassas

                                         Prince William
                                             County




                          Figure 3: Control Systems


2.2     Traffic Signal Maintenance

With all agencies experiencing increasing demands on their transportation infrastructure, as well
as their staff, maintenance is a critical element in the success or failure of their signal system
programs. There are several types of signal maintenance activities that a jurisdiction can
undertake. The three main categories include: 1) repair maintenance (malfunction and
breakdown), 2) preventive maintenance, and 3) response maintenance.

      1) Repair Maintenance covers two basic areas: malfunction and breakdown.

              a. Malfunction: any event that impairs the operation without losing the display and
                 sequencing of signal indications to approaching traffic. Malfunctions include



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                   timing failures, detection failures (vehicle and pedestrian), loss of interconnected
                   control, and other similar occurrences.

              b. Breakdown: any event that causes a loss of signal indication to any or all phases
                 or traffic approaches. Breakdowns include controller unit failures, controller
                 cabinet equipment failure, cable failures, loss of power, and signal lamp burnout,
                 leaving no indication visible.

      2) Preventive Maintenance: Checks and procedures to be performed at regularly
         scheduled intervals for the upkeep of traffic signal equipment. This includes inspection,
         cleaning, replacement, and record keeping.

      3) Response Maintenance: Procedures and repairs made in the event of reported failed
         traffic signal equipment and its restoration to safe, normal operation.

Benefits Of Maintenance Programs: Computerized systems and technology can reduce
demands on limited agency manpower, and improved design of these systems can further assist
an agency to offset system maintenance and related costs. Even with good system design, there
are even more significant benefits that can be gained through a formal, properly funded and
staffed maintenance program, regardless if an agency’s system is ―high tech‖ or not. On the
other hand, if signal maintenance is not performed on these systems consistently, negative
impacts can quickly result, including poor signal operations that can result in increased stops and
delay, vehicular and pedestrian safety concerns, unstable traffic flow, congestion, increased
emissions, etc.

2.3     Survey Results: Jurisdictional Signal Systems Programs

Seventeen agencies throughout Maryland, Northern Virginia, and Washington, D.C. are
responsible for the administration, implementation, operation, and/or maintenance of signal
systems. These agencies were recently interviewed to gather technical information on their
current signal system programs, as well as their thoughts and concerns on their systems’
effectiveness.

Sixteen of these agencies with operations and maintenance responsibilities are listed in
Tables 1 - 9, along with their systems’ attributes. Fairfax County, which allows the Virginia
Department of Transportation (VDOT) to operate and maintain its signals, is not included in the
table, but rather, is represented by VDOT.

Detailed summaries for each agency’s signal system program, can be found in Appendix A of
this document. These summaries are based on the survey responses received from agency
personnel.




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                                                                                                                                                                     Traffic Signal
                                                                                                                                  Optimization                       Management
                                       System Type               Operating System               Communications                     Software         Controllers    Support Software                             Other System Features

                                                                                             Copper             Fiber                                                                           Priority                     Detection
                                                                 OS/2
                             Central   Closed                     or        Win                                                                                                            Fire,                                     Microwave       Archive
                             Control    Loop         Hybrid      UNIX     95/98/NT      Own      Lease    Own      Lease        SYNCHRO    Other   NEMA     170   MONARC      Other       Rescue     Transit   Video   Loop        Infrared/Radar     Data

DCDPW/DCDOT                      X                     X           X          NT         X                                         X                         X               QuicNet        X              X

MDSHA                                     X                        X          NT         X                 X                       X                X                         ARIES         X              X    X        X

Montgomery County                X                               UNIX         NT         X            X    X                              Custom    X                       COMTRAC                        X    X        X        Microwave Radar

Prince Georges County                     X                                   NT                      X                 X         N/A       N/A     X                       Street-wise

Virginia DOT                     X                               OS/2         NT                      X                 X          X                X        X                MIST          X                            X           Microwave          X

Arlington County                 X                     X         OS/2       95, NT       X                                                SCOOT     X                X                      X          UW       X        X               Infrared       X
                                                                                                                                                                  (SCOOT)

Fairfax County                                                                                                                                                                              X

City of Alexandria                               Client server                NT         X            X                            X       TSP4     X               X                       X                   X        X                  X           X

City of Fairfax                           X                      OS/2                    X                                         X                X               X                       X                            X               Radar          X

City of Falls Church                             Time-Based        ?          ?          X                                         ?         ?      X                ?          ?           X                            X
                                                   Coord.

City of Frederick                         X                       N/A        N/A         X                                        N/A       N/A     X               N/A        N/A          X                            X                              X

Town of Herndon                          UW                                   NT        N/A       N/A     N/A           N/A                 UW      X                          Peak         X                  UW        X

Town of Leesburg                                       X                      NT        N/A       N/A     N/A           N/A               PASSER    X                        PASSER        UC                            X                              X

City of Manassas                                       X                      NT                                        X          X                X             VMS 330                   X                            X                              X

City of Manassas Park                                  X                      X          X                                        N/A       N/A     X                ?                      X                   X        X                              ?

City of Rockville                                      X                      98                      X                 X          X                X                          Aries                            X        X                             UW

Town of Vienna                            X                                 98, NT       X            X                 X                   LM      X                           LM                                       X
   Key:        N/A – Not Applicable           UW – Underway             ? – Information Not Available       UC – Under Contract                                                                                                          11/12/01 – MWCOG

                                                     TABLE 1: MWCOG Region Traffic Signal Systems - Signal System Features and Capabilities


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                                                  Control Systems                            Signal Optimization Software
                                        Central       Closed        Hybrid   Synchro   Scoot        Passer            Ot h e r        None
                                                       Loop
            DCDPW/DOT                                                            
            MDSHA                                                                
            Virginia DOT                                                         
            City of Alexandria                                                                                      TSP4
            Arlington Co.                                                                                         (UTCS)
            City of Fairfax                                                                                    (SIM Traffic)
            City of Falls Church                                             N/A      N/A            N/A              N/A             N/A
            City of Frederick                                                                                                          
            Town of Herndon                            UW                     N/A      N/A            N/A              N/A             N/A
            Town of Leesburg                                                                                     (NETSIM)
            City of Manassas                                                                                   (SIM Traffic)
            City of Manassas Park         ?             ?            ?            ?     ?              ?                ?
            Montgomery Co.                                                                                        Custom
            Prince Georges Co.                                                                                                         
            City of Rockville                                                    
            Town of Vienna                                                                                            LM

          N/A – Not Applicable
          UW – Underway
          ? – Information Not Available

                                              Table 2: Control Systems and Optimization Software




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                                    Free       F u lly -    Semi-     F la s h    T im e - b a s e d    Traffic     Traffic    T im e o f     Pre-Timed
                                  Operation   Actuated     Actuated               Coordination         Adaptive   Responsive      Day
       DCDPW/DOT                                                                                                                                
       MDSHA                                                                                                                 
       Virginia DOT                                                                                Testing      Testing
       City of Alexandria                                                              
       Arlington Co.                                                                                  
       City of Fairfax                                                                
       City of Falls Church                                                                                                      
       City of Frederick                                                                                             
       Town of Herndon                                                                                           
       Town of Leesburg                                                                  
       City of Manassas                                                                                             
       City of Manassas Park            ?         ?           ?          ?                ?               ?           ?            ?              ?
       Montgomery Co.                                                                                                                       
       Prince Georges Co.                                                                                                     
       City of Rockville                                                                 
       Town of Vienna                                                                 

      N/A – Not Applicable
      UW – Underway
      ? – Information Not Available

                                                            Table 3: Control Strategies




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                                                       Controllers                           Communications
                                             T yp e 170         NEMA     Copper*    Fiber*        L eased     Radio    T im e - b a s e d
                                                                                                   L in e s            Coordinators
                    DCDPW/DOT                                             
                    MDSHA                                                          
                    Virginia DOT                                    
                    City of Alexandria                                    
                    Arlington Co.                                         
                    City of Fairfax                                       
                    City of Falls Church                                  
                    City of Frederick                                     
                    Town of Herndon                                      N/A        N/A            N/A       Future          
                    Town of Leesburg                                 
                    City of Manassas                                                                                        
                    City of Manassas Park          ?                 ?     ?          ?              ?          ?
                    Montgomery Co.                                                               
                    Prince Georges Co.                                             UW
                    City of Rockville                                                              
                    Town of Vienna                                                                                         

                   N/A – Not Applicable
                   UW – Underway
                   ? – Information Not Available
                   * - Agency Owned’

                                                       Table 4: Controllers and Communications




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                                                         Monarc    M is t        Scoot   Passer   QuicNet     Ot h e r

                              DCDPW/DOT                                                             
                              MDSHA                                                                          ARIES
                              Virginia DOT                          
                              City of Alexandria             
                              Arlington Co.                                      
                              City of Fairfax                
                              City of Falls Church            ?      ?            ?        ?        ?            ?
                              City of Frederick              N/A   N/A           N/A      N/A      N/A         N/A
                              Town of Herndon                                                                TCT-LM
                              Town of Leesburg                                            
                              City of Manassas                                                              VMS 330
                              City of Manassas Park           ?      ?            ?        ?        ?            ?
                              Montgomery Co.                                                                COMTRAC
                              Prince Georges Co.                                                            Streetwise
                              City of Rockville                                                               Aries
                              Town of Vienna                                                                   LM

                             N/A – Not Applicable
                             UW – Underway
                             ? – Information Not Available

                                                     Table 5: Traffic Signal Management Software




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                                                        In d u c t iv e    Video   Microwave   M a g n e t ic   Radar   Infrared
                                                          Loops                                 Probes
                              DCDPW/DOT                                               
                              MDSHA                                                               
                              Virginia DOT                                                        
                              City of Alexandria                                      
                              Arlington Co.                                                                             
                              City of Fairfax                                                                   
                              City of Falls Church           
                              City of Frederick              
                              Town of Herndon                             UW
                              Town of Leesburg               
                              City of Manassas               
                              City of Manassas Park           ?             ?           ?            ?           ?         ?
                              Montgomery Co.                                                                 
                              Prince Georges Co.                                              Micro
                              City of Rockville                            
                              Town of Vienna                 

                             N/A – Not Applicable
                             UW – Underway
                             ? – Information Not Available

                                                                          Table 6: Detection




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                                                                          Op t i c a l    Push Button   Audible   GPS

                                         DCDPW/DOT                       (F&R, T)
                                         MDSHA                           (F&R, T)             (F&R)
                                         Virginia DOT                     (F&R)               (F&R)    (F&R)
                                         City of Alexandria                (F)
                                         Arlington Co.              (F&R, T-U)                (F&R)
                                         City of Fairfax                   (F)
                                         City of Falls Church              (F)
                                         City of Frederick                                      (F)
                                         Town of Herndon                                       (F&R)
                                         Town of Leesburg                    UW
                                         City of Manassas            (F&R, P)
                                         City of Manassas Park                ?                  ?         ?        ?
                                         Montgomery Co.                                         (F)               (T)
                                         Prince Georges Co.                                     (F)
                                         City of Rockville
                                         Town of Vienna
                                         Fairfax Co.                      (F&R)               (F&R)

                                        F – Fire
                                        R – Rescue
                                        T – Transit
                                        P – Police
                                        N/A – Not Applicable
                                        UW – Underway
                                        ? – Information Not Available

                                                                   Table 7: Preempt / Priority


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                                         WIN 3.1   WIN 95    WIN 98        WIN NT   OS/2   UNIX   VMS     DOS

               DCDPW/DOT                                                     
               MDSHA                                                                                      
               Virginia DOT                                                        
               City of Alexandria                                            
               Arlington Co.                                                                    
               City of Fairfax                                             Future   
               City of Falls Church           ?      ?         ?             ?       ?      ?      ?        ?
               City of Frederick              ?      ?         ?             ?       ?      ?      ?        ?
               Town of Herndon                                               
               Town of Leesburg                                              
               City of Manassas                                              
               City of Manassas Park          ?      ?         ?             ?       ?      ?      ?        ?
               Montgomery Co.                                                           
               Prince Georges Co.                                            
               City of Rockville                               
               Town of Vienna                                               

              N/A – Not Applicable
              UW – Underway
              ? – Information Not Available

                                                         Table 8: Operating Systems




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                                                                                       Data Archived?       Database Schema Available?

                             Oracle     SQL   DBase IV   SyBase        Ot h e r   Yes               No         Yes                 No
DCDPW/DOT                                                                                                                        
MDSHA                                                                                                         ?                   ?
Virginia DOT                                                                                                  
City of Alexandria                                                                                                               
Arlington Co.                                                                                                                    
City of Fairfax                                                                                               
City of Falls Church            ?        ?       ?         ?              ?                                                       
City of Frederick                                                                                                                
Town of Herndon                                                                                                                  
Town of Leesburg                ?        ?       ?         ?              ?                                                       
City of Manassas                                                                 
City of Manassas Park           ?        ?       ?         ?              ?        ?                    ?       ?                   ?
Montgomery Co.                                                                                               
Prince Georges Co.                                                                                                               
City of Rockville                                                      Access                                                     
Town of Vienna                                                                                                                   

N/A – Not Applicable
UW – Underway
? – Information Not Available

                                                     Table 9: System Databases




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2.4    Agency Comments On Signal Systems Operations

Overall, the majority of those agencies which have computerized systems have found that their
systems are easy to operate and user friendly, resulting in their ability to do their jobs in a more
proactive and efficient manner. Agency personnel feel that these systems and technologies
enable them to quickly respond to citizens’ complaints and system problems.

Staff engineers and technicians feel that these systems also make it easier to manipulate traffic
data and to more rapidly create (or modify) timing plans. The ability to remotely perform this
data collection, as well as the uploading and downloading of traffic signal timings to
intersections, is a major plus to optimizing traffic flow. Collection and utilization of real-time
traffic data offers significant benefits to the agencies, as they are able to gain more knowledge
and a better, more realistic understanding of the traffic demands on their roadway systems.

Staff from one Signals Operations Center indicated that their system has the capacity to provide
comprehensive failure reports for communications and controller status, system and local flash
operation, and status of system timing plans. This feature allows them to more accurately
determine system problems and in turn, provide better and more expedient response
maintenance.

Others noted that they like the variety of features found in their systems, such as the closed-loop
system operation, alternate phasing sequences, and transit priority control capabilities. These
additional features allow them to be more creative in finding solutions to traffic problems, and
also gives them the ability to assist a variety of transportation modes, such as transit, in providing
better service to their customers.

2.5    Agency Comments On Signal Maintenance Programs

Many agencies agree that having computerized systems help them tremendously in their
maintenance activities, as they are able to more quickly respond to repair needs (due to increased
accuracy in defining the problem). One agency noted that their maintenance costs have decreased
significantly (95%) due to their ability to replace computers more quickly and at lower costs.

Preventive Maintenance Programs: All of the agencies in the region with traffic signal
responsibilities have some form of a Preventive Maintenance program, although they vary
according to system size and sophistication, as well as maintenance staffing levels and schedules.

Some agencies in the region have no set schedule for preventive maintenance work, while others
have preventive maintenance work scheduled as frequently as every 90 days, others do the work
every six months, and still others schedule preventive maintenance annually or every two years.

Several agencies have defined schedules for certain pieces of equipment, such as signal heads
being replaced every two years and going into controller cabinets to do preventive maintenance
at least once a year. Still other agencies base their preventive maintenance schedules on field
versus system devices. For some, the goal is to do preventive maintenance work on field devices
annually, and system devices every two years.


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Contract maintenance is used by those agencies with limited maintenance staff. One agency
reported that while contract maintenance is conducted annually, their practice is that whenever a
signal is upgraded, the contractor is directed to check out everything related to that signal and to
repair anything needed at that time.

Response Maintenance Programs: All area jurisdictions responded that they have response
maintenance criteria to follow when dealing with repair calls. In response to the question of
―target times‖ for repairing non-functioning traffic signals, the answers varied based on signal
location and time of day. However, the general time range for response maintenance functions
runs from ―immediately‖ to 24 hours.

With regard to geographic location, for one agency, the response times vary from three hours if
the signal is in a downtown area, to five hours for those in residential areas.

For those that have time-of-day criteria, most stated that their target time ranges from
―immediately‖ and ―15 minutes‖ during business hours to ―longer after working hours.‖

One agency stated that their response maintenance was ―immediately, if not sooner. The longest
ever was two hours.‖

Some agencies noted that they have staff on 24-hour call for signal maintenance and this helps
them greatly in their efforts to be immediately responsive to traffic signal malfunctions or
breakdowns.

Signal Program Administration and System Constraints: Even with all of these technical
advantages and benefits, most agencies find that some limitations still exist in their signal system
programs. However, they recognize these as opportunities to creatively improve the systems in
order to do their jobs even more efficiently and effectively.

All agencies felt that additional staff support and funding would be extremely helpful, allowing
them to operate their systems in such a manner that they could perform even more traffic
management functions to assist in mitigating traffic congestion, unnecessary stops and delays.

Having additional technology resources was also noted as something that would be beneficial.
For example, some feel that video-based features (such as video detection and CCTV) would
allow agency personnel to better monitor traffic conditions and remotely adjust/change signal
timing, as needed. It is felt that this would be a more proactive and efficient way of addressing
traffic signal problems, instead of having to rely on citizens’ complaints and/or radio traffic
reports of malfunctioning signals. There are also issues with technology (controllers) becoming
obsolete, resulting in poor vendor support and increased costs.

Communications issues were noted by several agencies, from those who had no communications
infrastructure in place at all (but need it), to those who felt their system’s performance was
hampered due to communications bandwidth limitations.




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Custom features were also noted as potential trouble spots – one agency noted that the process to
create reports was cumbersome (due to a custom reporting feature), making the process time
consuming.

Desired Additional Program Administration and Signal System Features: While all agencies
are doing a great job with what they have, these transportation officials could do even more, if
additional resources were made available. Some of the features that agencies would like added to
their programs and systems include:

     More staff, in order to be more proactive and responsive in systems operations and
      maintenance (for example, increased staffing levels would enable the agency to perform
      signal retiming and optimization on a routine basis — to keep up with the real world
      fluctuations of traffic demand and citizens’ complaints)
     Closed circuit television for remote system monitoring (to include verification and resolution
      of traffic and system problems before going out into the field; e.g. immediate adjusting of
      signal timing during an incident or identification of a signal bulb outage)
     Video detection
     Access to more communications infrastructure with greater bandwidth capabilities
     Greater event tracking capabilities in the systems (created in a database format to enable
      query of activities)
     Ability to observe signal operations in an off-line format
     Communication between the on-street master controllers
     Expanded master controller capabilities and functions
     Better traffic signal coordination capabilities, specifically on side streets
     Improvement of traffic responsive features to make procedures less cumbersome
     Ability to review preemption information from a central location
     Capability to work directly with optimization software from the system.

Although the functional responsibilities and the technical complexity and size of each agency’s
systems vary, there is no doubt that each jurisdiction’s system functionality is very important and
plays a vital role in achieving the transportation goals of the regional transportation network.
These transportation agencies are operating and maintaining their systems to meet a
demonstrated need locally, while at the same time, also providing a valuable service and benefit
to the region.


3.0      OPPORTUNITIES FOR COLLABORATION/ IMPROVEMENT PLANS

While there are significant benefits to providing and conducting good traffic operations and
maintenance practices within a single jurisdiction, even greater gains can be achieved when State
and local transportation agencies jointly pursue and initiate collaborative efforts in traffic

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operations and maintenance across jurisdictional borders. Not only can these efforts maximize
the effectiveness of an agency’s limited resources, but they can also provide tremendous benefits
to the traveling public such as smoother traffic flow, and reduced delays and stops along a
corridor.

Opportunities for cooperation between State and local transportation agencies can take the form
of either technical or institutional collaboration, and can often be accomplished at very low (to
no) cost to an agency. Examples of technical collaboration include activities such as:

   Signal coordination on an arterial corridor across jurisdictional borders
   Signal timing optimization along a corridor.

For example, in order to move traffic smoothly along an arterial corridor that goes through more
than one jurisdiction, traffic engineers in neighboring jurisdictions may decide to coordinate their
traffic operations, e.g. use the same cycle length along the corridor.

Institutional collaboration can be accomplished between agencies in many ways, including:

   Joint procurement and possible sharing of signal equipment
   Development, endorsement, and implementation of similar signal timing plans
   Sponsor and conduct joint training courses for staff, and
   Knowledge transfer among staff.

An example of knowledge transfer could involve sharing the expertise of one agency’s staff in a
particular area. For example, many systems in the region utilize NEMA controller technology.
If there is a state or local traffic engineer or signal technician who has considerable experience
and expertise in the operations and maintenance of NEMA controllers, this knowledge and
wisdom could be shared with other agencies that may have limited or no staff with knowledge or
experience in this area.

As another example, joint training courses could be arranged for regional participants. The work
of MWCOG’s Professional Capacity Building Working Group could be used to identify joint
training needs and opportunities.

The Metropolitan Washington region has already recognized the tremendous benefit of
collaborative efforts in the area of traffic signals and systems. There are currently several
ongoing multi-jurisdictional traffic signal activities that promote regional objectives to improve
traffic flow and safety in the region. These efforts, facilitated by the Metropolitan Washington
Council of Governments, include the Pilot Arterial Corridor project, the regional traffic signal
problem reporting system website, and the Traffic Signal Preemption/Priority study. These
efforts all serve as models of collaborative regional efforts in which an agency can participate
with minimal disruption to its ongoing traffic signal system program.

Another potential area of collaboration involves traffic data. The majority of agencies surveyed
currently do some level of traffic data archiving, and the remaining agencies have plans to do so
in the future. This data is a valuable resource, not only to traffic signal-related functions, but

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also for regional transportation and land use planning activities and (as evidenced recently) in
incident and evacuation activities. Being able to share this data with minimal, if any, need for
database modifications would be of tremendous benefit to the region. Agencies could consider
utilizing database programs that ease the sharing of data across jurisdictional lines.

There are still other opportunities for collaboration worthy of review by area transportation and
other governmental agencies. A major goal for the Metropolitan Washington region is to
optimize traffic flow for all travelers. To that end, the majority of agencies surveyed have
underway (or will in the near future) programs geared towards optimizing signal timings to
improve traffic flow. This activity can yield tremendous ―bang for the buck,‖ being one of the
most cost-effective measures an agency can take using existing resources.

While this optimization is geared towards improving traffic flow for all travelers, state and local
agencies are also sensitive to the special traffic flow needs of their partners in the transit and
emergency services communities, and are seeking safe and efficient ways to assist them in this
area.

For example, the Metropolitan Washington region is becoming more and more transit-dependent
as single occupant vehicular (SOV) congestion continues to increase on the highway network.
Transportation officials feel that transit is a valuable alternative for travelers to consider to help
address this congestion problem, and recognize that providing reliable, high quality and
expedient transit service is a must to lure these travelers out of private automobiles.

With this in mind, traffic engineers throughout the region are exploring incorporating transit-
related features into their (current and future) signal systems. This includes utilizing system
hardware, software and/or communications features that can be easily adapted to assist in the
functionality of a current and future transit signal priority system and/or AVL transit fleet
activities.

These types of signal design considerations can also be applicable to any effort involving the
safe and efficient routing of emergency response vehicles, such as fire and rescue units, as well
as police. Many jurisdictions already have some basic level of preemption infrastructure in place
for these emergency responders. It is most likely that, as the public safety need increases and the
technology matures, these systems will also become a part of traffic signal system operations.

By considering transit and emergency services needs in the design, upgrade and operations
phases of signal systems, transportation agencies will be ensuring that technologies, systems, and
organizations work together in a safe and cost-effective manner to accomplish the individual
jurisdictions’ goals, as well as the region’s goals.

Integrated Traffic Management Systems (ITMS) is the next technological phase for many
transportation agencies around the country — and the Metropolitan Washington region is part of
this evolution. The District of Columbia Department of Public Works currently has an ITMS
initiative underway, which will integrate their arterial and freeway management operations (as
well as some emergency services functions) into one center.



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Likely candidates for future potential opportunities involve those agencies that have both signal
systems and freeway management system operations, e.g., CHART and Montgomery County’s
ATMS, as well as VDOT’s Northern Virginia District Smart Traffic Center and its Traffic Signal
System.


4.0      CONCLUSIONS

All of the transportation agencies throughout the Metropolitan Washington region are taking
tremendous advantage of the evolution of computer technology and using it to more efficiently
and effectively operate and maintain their traffic signals and systems. In addition to this
observation, several other conclusions were drawn based on the survey data.

Throughout the Metropolitan Washington region, significant coordination of traffic signals
occurs, both within individual jurisdictions and between regional partners. There are currently
several ongoing multi-jurisdictional traffic signal activities that promote regional objectives to
improve traffic flow and safety in the region. These efforts, facilitated by the Metropolitan
Washington Council of Governments (MWCOG), include the Pilot Arterial Corridor project, the
regional traffic signal problem reporting system website, and the Traffic Signal
Preemption/Priority study. From these activities, many regional partners have discovered
unexpected similarities in their signal systems.

Each jurisdiction is trying to optimize the use of technology to save money. Integrated Traffic
Management Systems (ITMS) is the next technological phase for many transportation agencies
around the country and the Metropolitan Washington region is a part of this evolution. The
District of Columbia Department of Public Works currently has an ITMS initiative underway
which will integrate their arterial and freeway management operations into one center (as well as
some emergency services functions).

All of the transportation agencies throughout the Metropolitan Washington region are taking
tremendous advantage of the evolution of computer technology and using it to more efficiently
and effectively operate and maintain their traffic signals and systems. Common applications of
technology include the use of NEMA and Type 170 controllers and SYNCHRO optimization
software, as well as system data archiving activities.

The region is performing well under difficult circumstances. In the face of limited staffing and
funding, transportation agencies’ staff continues to find creative ways to use technology to help
save time and money, as well as to maximize their limited dollars and staff - especially in the
area of signal maintenance.

The region could perform better with additional resources. While all agencies are doing a great
job with what they have, these transportation officials could do even more, if additional
resources were made available, including:

     More staff, in order to be more proactive and responsive in systems operations and
      maintenance (for example, increased staffing levels would enable the agency to perform


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    signal retiming and optimization on a routine basis — to keep up with the real world
    fluctuations of traffic demand and citizens’ complaints)
   Closed circuit television for remote system monitoring (to include verification and resolution
    of traffic and system problems before going out into the field; e.g. immediate adjusting of
    signal timings during an incident or identification of a signal bulb outage)
   Video detection
   Access to more communications infrastructure with greater bandwidth capabilities
   Greater event tracking capabilities in the systems (created in a database format to enable
    query of activities)
   Ability to observe signal operations in an off-line format
   Communication between the on-street master controllers
   Expanded master controller capabilities and functions
   Better traffic signal coordination capabilities, specifically on side streets
   Improvement of traffic responsive features to make procedures less cumbersome
   Ability to review preemption information from a central location
   Capability to work directly with optimization software from the system.

While facing the everyday reality of limited staffing and funding resources, these agencies still
manage to take a proactive approach to traffic management by utilizing a variety of tools to
mitigate the effects of increasing vehicular, bicycle, and pedestrian demands on the limited
capacity transportation facilities in the region.

Although the functional responsibilities and the technical complexity and size of each agency’s
systems vary, there is no doubt that each jurisdiction’s system functionality is very important and
offers a valuable service to the transportation goals of the regional transportation network. These
transportation agencies are operating and maintaining their systems to meet a demonstrated need
locally, while at the same time, also providing a valuable service and benefit to the region.

Traffic signals are an everyday occurrence for many travelers in the Metropolitan Washington
region; therefore, it is of the utmost importance that traffic engineers and signal technicians make
every effort to ensure that these devices are being operated and maintained to the highest
possible degree of safety and efficiency.




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APPENDIX A: NARRATIVE SUMMARY OF AGENCY SURVEY RESULTS

DISTRICT OF COLUMBIA DEPARTMENT OF PUBLIC WORKS/DOT

The Washington, DC Signal Operations Center (SOC) is located in the Public Works
Department. There are 25 staff-persons who operate and maintain the central control system (10
field technicians, five office personnel and 10 consultants who are engineers and technicians).
The system includes 1,500 traffic signals that function in fully-actuated, time-based coordination
and/or pre-timed mode. It is estimated that five to ten traffic signals are added to the system each
year. Type 170E controllers are currently used, but the agency is transitioning to 2070E. There
are 500 inductive loops, three video detection and 100 microwave detection devices. Fifty
percent of system detection is on-line using agency-owned copper lines. (The plan is to go to all
fiber in the future).

QuicNet 4.0 is the software application that is used to support the management of the traffic
signal system. The agency uses a Windows NT operating system, with a LAN network and
TCP/IP protocol. An SQL database archives system data but a copy of the agency’s database
schema is not available. The hardware used to operate the system includes six IBM Netfiniti
servers with ten operator interfaces, using 256M of RAM with a hard disk size of 30GB. The
central processing units (CPU) operate at a speed of 500 MHz. The system provides remote dial-
in capabilities using landlines. Currently, the District has plans to do a complete system upgrade.

A priority control system for Fire and Rescue, as well as police operations, is in place (42 optical
units); fire and EMS personnel have access to these devices. There are three vehicles with
AVL/GPS capabilities. There are 40 Opticom units installed for transit priority, mostly along
Georgia Avenue (no GPS capabilities). There are twelve closed circuit television (CCTV)
cameras currently in operation, with plans to install three hundred more cameras in the future.


MARYLAND STATE HIGHWAY ADMINISTRATION

The Signal Operations Center (SOC) and the Statewide Operations Center are located at the
Office of Traffic Safety, in Hanover, Maryland. The Signal Operations Section contains
approximately 40 field technicians who operate and maintain the SHA's network of traffic
signals and traffic signal systems. This network includes approximately 1500 traffic signals
operating in either "free" (fully actuated) mode, time-based coordination, or as part of a closed
loop system. Approximately 50 new traffic signals are added to the system each year, using
NEMA controllers. The closed loop systems contain approximately 1000 inductive "sampling
loops" used for system data collection.

The agency’s operating system is DOS, Windows 3.1 and Windows NT, with an Oracle database
(system data is archived). The network is Netware and Windows NT-based, using IPX and
TCP/IP protocols. There are approximately four operator interfaces. SYNCHRO is the software
application used for optimization. The system has remote dial-in capabilities utilizing agency-
owned fiber and copper lines, as well as cellular communication.



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Preemption/priority control devices (250 optical and 100 push button) are deployed by the
agency for fire and rescue services. Priority control devices (50 optical) are deployed by the
agency for transit operations. There are no GPS capabilities associated with either the
preemption or priority control devices at this time.

Approximately 100 intersections are now using video detection technology, with an additional
100 to have video detection installed shortly.


VIRGINIA DEPARTMENT OF TRANSPORTATION

The Northern Virginia District Traffic Signal System (NOVA TSS) is located in Arlington,
Virginia. There are 45 employees assigned to the TSS (28 field technicians and 17 control room
staff) to operate and maintain the central system, which includes 946 traffic signals running in
free operation (fully and semi-actuated) and time-based coordination modes (also, testing traffic
adaptive and traffic responsive modes). It is estimated that 50 traffic signals are added to the
system each year. NEMA and Type 170 controllers are in use (though VDOT is in the process
of replacing all NEMA controllers with Type 170s). There are 10,000 inductive loops,
25 microwave detectors, and 4 magnetic probe devices deployed in the field. Ninety-eight
percent of the detection is on-line using leased lines.

MIST is the software application that is used to support the management of the traffic signal
system. The hardware used to operate the system includes nine servers (8 Dell, 1 DEC Alpha),.
The servers’ central processing units (CPU) run at 450Mhz, with 256MB/1GB of Random
Access Memory (RAM) and 27GB of hard drive space. There are 14 personal computers (Dell
Optiplex); eleven operating at a CPU speed of 450Mhz and 3 at 400 MHz. They are equipped
with 256MG of RAM and 9GB of hard drive space. Four workstations (Dell Precision) operate at
a CPU speed of 450MHz, with 1GB of RAM and 9GB of hard drive space. There are 30
operator interfaces.

The agency’s operating systems are Windows NT and OS/2 (soon NT only). The database
application is Sybase (the database schema is currently available). The network is OS/2 (LAN
server) and NT, using the TCP/IP protocol. SYNCHRO is the software application used for
signal optimization (system data is archived for future use). The system provides remote dial-in
capabilities using landlines. Currently, VDOT has plans to upgrade the operations center
equipment (25% equipment replacement per year based on useful life of five years; all
equipment recently upgraded in March 1999).

There are no closed circuit television (CCTV) cameras in use by the TSS. Preemption/priority
(optical, audible and push button) are in use for Fire & Rescue operations and is deployed at the
Lansdowne Hospital entrance. There are no GPS capabilities or preemption/priority strategies for
transit operations.




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CITY OF ALEXANDRIA, VIRGINIA

The Signal Operations Center (SOC) is located in the City Hall Building in Alexandria, Virginia.
Approximately 5 field technicians and 3 control room employees operate and maintain the closed
loop system, which includes 230 traffic signals running in free operation (fully actuated) and/or
time-based coordination mode. It is estimated that five to ten traffic signals are added to the
system each year. NEMA, NEMA-TS2-1, and NEMA-TS2-2 controllers are used. There are 560
inductive loops, 20 microwave detectors, and 3 devices for video detection.

MONARC is the software application that is used to support the management of the traffic signal
system. The hardware used to operate the system includes two Compaq servers, four Dell
personal computers, and one Compaq workstation; there are three operator interfaces. The
agency’s operating system is Windows NT and the database is SQL compliant (the database
schema is not available). The network information was not available but the agency is using the
TCP/IP protocol. TSP4 is the optimization software used by the City; if volume information is
available, SYNCHRO 4.0 is also used for signal optimization (system data is archived for future
use). The system provides remote dial-in capabilities using agency-owned twisted pair copper
landlines.

Currently, the City does not have plans to upgrade the operation center equipment, as a recent
replacement was just completed. Four Closed Circuit Television (CCTV) cameras, manufactured
by Pelco, are used at selected intersections throughout the City. In addition, preemption/priority
devices (15 optical) for Fire & Rescue operations are deployed, with the Fire Department having
access. There are no GPS capabilities or preemption/priority strategies for transit operations.


ARLINGTON COUNTY, VIRGINIA

The Signal Operations Center (SOC) is located in the Traffic Engineering Division of the
Department of Public Works in Arlington, Virginia. Approximately 7 field technicians and 2
control room operators operate and maintain the hybrid control system, which includes 248
traffic signals running in free operation (semi-actuated); time based coordination; and/or traffic
adaptive modes. It is estimated that four traffic signals are added to the system each year.
NEMA-TS2-1 and NEMA-TS2-2 controllers are used by the County. There are 190 inductive
loops, one infrared detector, and one device for video detection. Ninety-five percent of the
system detection is on-line using agency-owned copper lines.

MONARC and SCOOT are the software applications used to support the management of the
traffic signal system. The hardware used to operate the system includes three Pentium II
personal computers (PC), and four Pentium II workstations. The central processing units (CPU)
for the workstations run at 350MHz, with 96MB of Random Access Memory (RAM) and 8.4GB
of hard drive space. The three personal computers function as system servers, which operate
using the following:

1. MONARC (fixed time system) using a Pentium II processor with a CPU speed of 350MHz,
   64MB of RAM, and 4.3GB of hard drive space.


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2. SCOOT (traffic adaptive system) using a 433MHz DEC Alpha CPU, with 128MB of RAM
   and 4.3GB of hard drive space.
3. SCOOT (communications server) using a Pentium II processor with a CPU speed of
   350MHz, 128MB of RAM, and a 9.1GB SCSI hard drive.

The agency’s operating systems are Windows NT, OS/2, VMS, and Windows 95. The database
is SQL compatible (the database schema is not currently available). The network is OS/2 and
Windows NT, using NETBIOS/NETBEUI and TCP/IP protocols. The UTC system with a
SCOOT model attached to it is the software application used for signal optimization (system data
is not archived). There are presently six operator interfaces. The system provides remote dial-in
capabilities using agency-owned copper landlines. Currently, the SOC does not have plans to
upgrade the operation center equipment.

Preemption/priority devices for Fire and Rescue operations are deployed at twelve intersections
(10 push button and two optical). There are no GPS capabilities or preemption/priority strategies
for transit operations at the present time; however, the County is in the process of putting transit
priority on Columbia Pike. No CCTV is currently in place.


FAIRFAX COUNTY, VIRGINIA

VDOT owns and maintains the signal systems in Fairfax County. However, the County does
have a computer terminal where it can access traffic signal and traffic count data. The County
suggests timing changes to VDOT and works with the Traffic field operations group on traffic
signalization safety issues. The County does provide funding for traffic signals and developers
are also required to install new signals that are related to their development, or to escrow the
monies towards a future signal. Only two (2) counties in the Commonwealth of Virginia control
their own signals; one is Arlington County.

Fairfax County currently deploys preemption/priority devices – four (4) optical, 16 push buttons,
and four (4) which are a combination of optical and push button. Agencies with access to the
preemption are Fire and Rescue, including EMS and Suppression units. The County currently
has no transit-based preemption/priority but is experimenting with a system on U.S. Route 1.


CITY OF FAIRFAX, VIRGINIA

The City of Fairfax, Virginia operates its own traffic signal system. The City maintains an
operations center at the Property Yard located at 3410 Pickett Road. Seven crew maintain signs
and signals and one supervisor oversees the operations. The supervisor performs signal timing
and optimization functions. The City has recently assigned a staff member to assist the
supervisor on a part time basis to help perform optimization. The City operates approximately
50 traffic signals and adds on average one new signal each year.

The City of Fairfax operates a closed loop system. MONARC is the software application used to
support the management of the signal system. SYNCHRO is used for signal optimization. The

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computer used to manage the signal system is an OS/2 based personal computer. The City is
upgrading to a windows based operating system. The City does not normally archive data but
will perform data archiving on special request. The City uses priority/preemption at four major
intersections for fire and emergency vehicles.


CITY OF FALLS CHURCH, VIRGINIA

Signals are operated by the City of Falls Church in Falls Church, Virginia (though there is no
actual Signal Operations Center building in place). Approximately 1.5 staff persons operate and
maintain the hybrid system, which include 30 traffic signals running in time-based coordinated
mode, using NEMA controllers. No traffic signals are added to the system each year. There are
110 inductive loops in operation. Only two traffic signals are on-line using agency-owned
copper.

A single personal computer is used to operate the system; no other system information is
available. SYNCHRO 4.0 is the software application used for signal optimization (system data
is not archived and a database schema is not available). The system provides remote dial-in
capabilities using agency-owned copper landlines. Currently, there is no plan to upgrade the
signal operation equipment.

There are no Closed Circuit Television (CCTV) cameras in use. Preemption/priority (four units)
for Fire operations are deployed. There are no GPS capabilities or preemption/priority strategies
for transit operations.


CITY OF FREDERICK, MARYLAND

Signal operations duties are handled in Frederick, Maryland, with a signal operations center
under development. Approximately 14 staff members operate and maintain the closed loop
system, which includes 72 traffic signals running in time based coordination and/or traffic
responsive mode (plus actuation). All of the downtown area is under closed loop operation. It is
estimated that two traffic signals are added to the system each year, using NEMA controllers.
Agency-owned copper is presently assigned for use on the closed loop system (also one radio
link). There are 90 inductive loops, with none of the detection presently on-line (but plans are
underway to put them on-line and is estimated to be completed one year from now).

No software application is presently used for the management of the traffic signal system. No
detailed hardware or network information was provided.

 Information on the agency’s operating system was not provided. The database application
utilized is Hanson (the database schema is not currently available). The system does not
currently include remote dial-in capabilities.

Currently, plans are under development for an SOC with servers, fiber connections and
eventually CCTV cameras. Preemption/priority (one push button) for Fire operations is deployed


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at the Fire Department. There are no GPS capabilities or preemption/priority strategies for
transit operations.


TOWN OF HERNDON, VIRGINIA

The Signal Operations Center (SOC) is located in Herndon, Virginia. Two staff members are
assigned to operate and maintain the signal system, which include 30 traffic signals running in
time-based coordination mode. The closed loop system is under construction and should be
completed by late summer/early fall. It is estimated that one to two traffic signals are added to
the system each year. NEMA TS-1 controllers are used, with 325-350 inductive loops in
operation; video detection is to be added at one intersection soon. None of the detection is
currently on-line; field site visits are required to download the data.

An old DOS-based version of Peak’s closed loop system software is the application that is used
to support the management of the traffic signal system. Pentium computers are proposed for the
new system, with the central processing units (CPU) operating at speeds of 166Mhz, with 64 Mb
of Random Access Memory (RAM) and 2GB of hard drive space. There are two operator
interfaces in the system.

The database is SQL compatible (the database schema is not available). Currently, the system
data is not archived. There are plans underway for the upgrade of the SOC equipment. The new
equipment will include a closed-looped system, with the communications medium obtained
through the use of radios transmitting on fixed frequencies (frequencies have already been
obtained by the FCC).

Preemption/priority (one push button) is deployed for Fire and Rescue services. There are no
GPS capabilities or preemption/priority strategies for transit operations. Closed Circuit
Television (CCTV) cameras are not currently in use.


TOWN OF LEESBURG, VIRGINIA

The Town manages the traffic signal system functions in Leesburg, Virginia (currently no signal
operations center built). One full-time traffic engineer maintains the hybrid signal system, which
includes 22 traffic signals running in time-based coordination mode (with internal time clocks).
It is estimated that two traffic signals are added to the system each year. NEMA controllers are
used, with inductive loops in operation. None of the detection is currently on-line, as there
presently is no signals communications infrastructure in place. (The town has funds for a
communication system but not put out for bid yet).

PASSER is the application that is used to support the management of the traffic signal system.
While there are plans to build an SOC, only laptops are currently used to upload and download
signal timings and change and coordinate program values and settings. The agency’s operating
system is Windows NT and system data is archived regularly (the database schema is not
available).


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Closed Circuit Television Cameras (CCTV) and preemption/priority devices are not currently in
use, although there is a contract under development that will put in preemption/priority devices
for Fire and Rescue services at five intersections next summer.


CITY OF MANASSAS, VIRGINIA

The Signal Operations Center (SOC) is located in the Public Works Department, in Manassas,
Virginia. Approximately 2 field technicians and 1 control room operator (Director and Lead
Technician share this role) maintain the hybrid system, which include 45 traffic signals running
in time based coordination, traffic responsive (only on one corridor) and/or free operation at
night (fully-actuated). It is estimated that two traffic signals are added to the system each year.
NEMA-TS2-1 controllers are used. There are 600 inductive loops, 1 infrared detector, and 1
device for microwave detection. 95% of the detection is on-line using agency- owned fiber lines.

IDC VMS 330 is the software application used to support the management of the traffic signal
system. The hardware used to operate the system includes two 486 servers. The agency’s
operating system is Windows NT, using NETBIOS protocols. SYNCHRO is the software
application used for signal coordination and optimization (system data is archived for future use
and a copy of the agency’s database schema is available). The system provides remote dial-in
capabilities using landlines. Currently, the SOC has plans to upgrade the operation center
equipment within the next year.

Opticom preemption/priority devices for Fire/Rescue and Police operations are deployed on all
signals (for use by surrounding jurisdictions as well). There are no GPS capabilities or
preemption/priority strategies for transit operations, and Closed Circuit Television Cameras
(CCTV) are not currently deployed.


CITY OF MANASSAS PARK, VIRGINIA

Signal operations are conducted in the City of Manassas Park, Virginia. Three and one-half staff
members are assigned to operate and maintain the signal system, which includes six traffic
signals running in free operation mode. The signals are a part of a closed loop system. No traffic
signals are added to the system each year. NEMA controllers are used, with 20 inductive loops
in operation as well as eight (8) video detection units. One intersection is currently on-line via a
dial-in landline.

The City uses a Windows-based operating system. No network protocol, operator interfaces or
servers currently exist. WinTV software is used for the video, and Econolite's proprietary
software in conjunction with WinTV. Pentium computers are used in the system.

There currently is no system database; therefore, a database schema is not available and no
system data is archived. There are no plans underway for the optimization of the signal system.



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The communications medium is copper wire. The City plans to upgrade its operation center
equipment eventually, within the next five to seven years.

Preemption is deployed for Fire and Police services at four (4) intersections but with no GPS
capabilities. There are no preemption/priority strategies for transit operations. Eight (8) Econolite
Closed Circuit Television (CCTV) cameras are currently in use.


MONTGOMERY COUNTY, MARYLAND

The Signal Operations Center (SOC) is located in the Traffic Management Center (TMC) in the
Department of Public Works and Transportation, in Rockville, Maryland. Approximately six
control room operators and 20 field technicians operate and maintain the central (hybrid) control
system, which includes 748 traffic signals running in free operation (fully and semi-actuated);
time of day; and/or traffic responsive modes. It is estimated that 6-10 traffic signals are added to
the system each year, using NEMA and NEMA-TS2-2 controllers. There are 1000’s of inductive
loops, approximately 24 microwave detectors, 30 devices for video detection, and several
magnetic probe and radar devices. Over one thousand (1000) sampling detectors are on-line
using agency-owned copper, fiber lines and leased lines.

A COMTRAC system using Fortran/Assembler language programs (running a data general mini
computer operating system, utilizing DT-200 communications over FSK 1800 baud) is used to
support the management of the traffic signal system. The hardware used to operate the system
includes Unix Sun Sparc servers and workstations, Windows 95, 98 and 2000, Data General
MV9600a, sun ULTRA Sparc servers, and Linux computers. The central processing units (CPU)
for workstations run from 75MHz to 500MHz for PC’s and 300+MHz Sun Sparc, with 32Mb-
1Gb of Random Access Memory (RAM) and 1 Gb-60Gb of hard drive space. There is RAID
systems and disk arrays that can store a half a terabit worth of data for archive, backup and
online needs.

The agency uses Windows NT, UNIX, and Windows 95-98 operating systems. The database is
Informix SQL (the database schema is available). The network uses TCP/IP protocols (system
data is archived). The system provides remote dial-in capabilities using land and cellular
(Virtual Private Network – VPN) lines. Currently, the TMC has plans to upgrade the operation
center equipment beginning within the next 6 months (upgrade to some servers and workstations
to a Windows 2000 platform, enhance and upgrade the Unix servers as well).

Preemption devices are deployed at twenty intersections (push buttons in the fire house) for Fire
services. There are also priority request devices on all of the Ride On transit vehicles, with GPS
capabilities. One hundred and thirty (130) CCTV cameras, manufactured by Diamond Electric,
are in operation.




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PRINCE GEORGES COUNTY, MARYLAND

The Signal Operations Center (SOC) is located in Prince Georges County, Maryland.
Approximately four field technicians and two system operators operate and maintain the closed
loop system, which includes 150 traffic signals running in free operation (fully and semi-
actuated), time of day, and/or time base coordination mode. It is estimated that three traffic
signals are added to the system each year, using NEMA controllers. There are over 1200
inductive loops, 12 video detection units, and 10 magnetic loops. Ninety percent of the detection
is on-line using agency-owned lines.

Streetwise by Naztec Inc is the software application used to support the management of the
signal system. The hardware used to operate the system includes two Dell computers. The
central processing units (CPU) for workstations are Pentium II, running at 300MHZ, with
128Mb of Random Access Memory (RAM) and 6.4 Gb of hard drive space.

The agency’s operating system is Windows NT. The County has no network at this time,
although future plans call for a Windows NT platform. The database is dBase IV (the database
schema is not currently available). System data is not currently archived. The County currently
does not have a network but there are plans to acquire one. The system provides remote dial-in
capabilities using landlines. Currently, there are plans to upgrade the SOC equipment within the
next year.

One pushbutton preemption device is deployed at one firehouse location No CCTV is currently
in place but there are plans to install one unit within the year.


CITY OF ROCKVILLE, MARYLAND

The City’s Signal Operations Center (SOC) is located in Rockville, Maryland. One office and
two field staff persons operate and maintain the hybrid signal system, which includes 39 traffic
signals running in time-based coordination mode. It is estimated that two traffic signals are
added to the system each year. NEMA controllers are used, with 35 inductive loops and five
video detectors in operation. Ninety percent of the detection is on-line using leased lines.
Remote dial-in capability exists over landlines.

Aries is the software application that is used to support the management of the traffic signal
system. Personal computers are used to upload and download signal timings and change and
coordinate program values and settings. The agency’s operating system is Windows 98, and
system data is not currently archived. The agency’s database schema is not available. There are
plans to upgrade the operation center equipment (the goal is to eventually monitor traffic using
cameras from the office). Preemption/priority devices and Closed Circuit Television Cameras
(CCTV) are not currently in use.




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TOWN OF VIENNA, VIRGINIA

The Signal Operations Center (SOC) is located in Vienna, Virginia. One staff person operates
and maintains the closed loop signal system, which includes 14 traffic signals running in free
operation (fully and semi-actuated) and/or time-based coordination mode. No traffic signals are
added to the system each year. NEMA controllers are used, with 93 inductive loops in operation.
None of the detection is currently on-line; but a technician can monitor this from the master
controller in the field.

LM System is the software application used to support the management of the traffic signal
system. Two personal computers are used to upload and download signal timings and change
and coordinate program values and settings. System data is not archived and the agency’s
database scheme is not available. Remote dial-in capability exists but is not functional at this
time. There are plans to upgrade the operation center equipment in two years.

Preemption/priority devices and Closed Circuit Television Cameras (CCTV) are not currently in
use.




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GLOSSARY

Actuation: the operation of any type of detector. The word ―operation‖ means an output from
the detector to the controller unit.

Adaptability: the quality of a traffic control system to maintain system operations over an
extended time period under changing conditions.

Arterial System: a linear sequence of signals on an arterial supervised to provide progressive
flow.

Arterial System Control: a type of control applied to two or more traffic signals to ensure
progressive traffic flow.

Bus Priority: cycle-by-cycle timing of a traffic signal so the beginning and end times of green
may be shifted to minimize delay to approaching buses. The normal sequence of signal displays
is usually maintained.

Closed Loop Signal System: a system that provides two-way communication between the
intersection signal controller and its master controller. The master controller communicates to
the signal operations center.

Coaxial Cable (coax): a broadband communications technology with the capability of carrying
many channels to transmit either data or video. Contains a single central conductor having a
common axis with a second outer conductor.

Communication Link: the means of connecting one location to another in order to transmit and
receive data.

Communication Network: a composite of communications links

Communication System: the composite of communications links and associated
communications equipment, which interconnect all the control and surveillance components of a
traffic control system.

Conflict Monitor: an electrical device that checks the green and yellow indications for each
phase to protect against improper conflicting signals. Provides an output in response to conflict.

Congestion: a freeway condition where traffic demand exceeds roadway capacity. Normally
occurs during peak travel periods or when a traffic incident reduces capacity by creating a
bottleneck.

Controller Assembly: a complete electrical mechanism mounted in a cabinet for controlling the
operation of a traffic control signal.

Controller Hardware – Solid State: solid-state controller assemblies include the controller unit,
conflict monitor, auxiliary devices and terminals.



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Controller Unit: the part of the controller assembly that performs the basic timing and logic
functions.

Coordination: the establishment of a definite timing relationship between adjacent traffic
signals.

Cycle: in a pre-timed controller unit, a complete sequence of signal indications. In an actuated
controller unit, a complete cycle is dependent on the presence of calls on all phases.

Cycle Length: the time required for one complete sequence of signal phases.

Dedicated Lines: communication lines used solely to interconnect two or more locations not
normally switched.

Detector: a device for indicating the presence or passage of vehicles or pedestrians. This general
term is usually supplemented with a modifier, i.e., loop detector, magnetic detector indicating
type.

Downloading: a function of a traffic system whereby the master controller can access the local
controller’s memory to update or modify a stored timing plan or controller settings.

Emergency Vehicle Preemption: the transfer of the normal control of signals to a special signal
control mode for emergency vehicles.

Fiber Optics: a broadband communication technology based on an optical waveguide that
channels the light in the fiber with total internal reflection at the boundary.

Flow Rate: number of vehicles passing a point on the roadway during a specified time period.

Fully-Actuated Control Assembly: a type of traffic-actuated controller assembly in which
means are provided for traffic actuation on all approaches to an intersection.

Incident: an occurrence in a traffic stream that causes a reduction in capacity or abnormal
increase in demand. Common incidents include accidents, stalled vehicles, spilled loads, etc.

Inductive Loop Detector: a pavement installed active device that senses a decrease in loop
inductance during vehicle presence.

Infrared Detector: passive and active above-ground mounted devices used for pedestrian and/or
vehicle presence. Some devices provide counts, speed, length, and queue.

Integrated Traffic Management System (ITMS): the system that integrates all hardware and
software elements of transportation management within a geographical region. It includes: traffic
signal systems; freeway management systems; traveler information systems; and incident
management systems.

Interconnected Signal System: a number of intersections that are connected by wire, radio, or
some other means to effect traffic progression.


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Isolated Local Controller: a local controller that is a stand-alone unit and a unit times right-of-
way assignments independently of other controllers.

Local Controller Assembly: a controller assembly supervising the operation of traffic signals at
a single intersection.

Local Controller: Pre-Timed: a device that controls all timing intervals to a fixed pre-
determined plan. Works best where traffic is predictable and constant.

Local Controller: Full-Actuated: a device that controls the length of all timing intervals based
on detected traffic demand on the associated approach. Adjusts cycle and split to fit changing
demands.

Local Controller: Semi-Actuated: a device that controls some approaches on the basis of
detected traffic demand. Non-actuated phases receive a minimum green interval that extends
until interrupted by actuation on other phases.

Local Signal Preemption: the emergency or transit vehicle transmits a signal to the intersection
controller where a special control phase assigns right-of-way.

Magnetic Detector: a pavement installed device of coiled wire with a highly permeable core.
Vehicle induced flux changes cause an induced voltage pulse. Not to be confused with a
magnetometer detector.

Magnetometer Detector: a pavement installed device that detects change in the vertical
component of the earth’s magnetic field caused by the presence of a vehicle. Not to be confused
with a magnetic detector.

Master Controller Assembly: a controller assembly for supervising multiple secondary
controller assemblies and/or multiple sub-master controller assemblies.

Model (type) 170 Controller: one of two types of the most commonly installed and available
intersection controllers. Specifications jointly developed by California and New York.
Specifications include sections on electronic modules, connectors, wiring, harnesses, and cabinet
enclosures.

Model 2070 Advanced Transportation Controller: the next generation of traffic signal
controller under the Model 170 line. A microprocessor based controller using OS-9 real-time
operating system, with VERSA Module Eurocard (VME) backplane and Motorola 680X0
processor family.

NEMA Controller: The second of the two most commonly installed and available intersection
controllers. Adopted by electrical equipment manufacturers.

Network Signal Control: control techniques that are applicable to a signalized roadway grid
network. Grid network imposes control constraints including common cycle lengths and closed
loop sum of offsets that must be an integral number of cycle lengths.


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Offline: descriptive of a system, peripheral equipment, or a process not under the control of a
central processing unit.

Online: descriptive of a system, peripheral equipment, or a process under the control of a central
processing unit.

Optimization Programs: programs that compute and evaluate the effects of various sets of
signal timing on vehicle flow within a given network. These programs determine optimal timing
plans and/or evaluate a given timing plan.

Phase: the portion of a traffic cycle allocated to any single combination of one or more traffic
movements simultaneously receiving the right-of-way during one or more intervals.

Phase Sequence: a predetermined order in which the phases of a cycle occur.

Preemption: the transfer of the normal control of signals to a special signal control mode.

Preemption/Priority Systems: preemption control of normal signal timing plans applies in the
following situations: signals adjacent to railroad crossings; emergency vehicle priority movement
and priority for transit vehicle. Preemption occurs on a single cycle basis.

Preemptive Devices: provide priority for fire and emergency vehicles by detecting the vehicle
and sending the preemption command to the controller.

Pre-Timed Controller Assembly: a controller assembly for the operation of traffic signals with
predetermined fixed cycle lengths, fixed interval duration, and fixed interval sequence.

Probe: the sensor form that is commonly used with a magnetometer-type detector.

Progression: term used to describe the progressive movement           of traffic through several
intersections within a control system without stopping.

Radar/Microwave Detectors: pole-mounted radar device that can sense speed and passage
and/or presence, when activated by a vehicle passing through its RF field.

Radio Communication: radio frequency transmission using any one of the following
techniques: cellular networks; satellite transmission; packet radio; and spread spectrum radio.

Sampling Detector: any type of vehicle detector used to obtain representative traffic flow
information.

Semi-Actuated Traffic Controller Assembly: a type of traffic-actuated controller assembly in
which means are provided for traffic actuation of one or more, but not all, approaches to an
intersection.

Signal Timing: the amount of time allocated to each interval/function in a signal cycle.




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Supervisory Local Controller: a control device ranging from a time-base coordination unit to a
remote master controller that determines or alters interval duration and/or maintains timing
relationships in a group of local controllers.

Sync Pulse: a pulse generated from a central point that provides a common time base to all
coordinated traffic controller units and which is used to provide a smooth flow of traffic through
coordinated intersections.

Time-Base Signal Coordination: a controller technique that changes timing plans on an internal
time basis.

Time-Based Coordination (TBC) Control: TBC control permits system operation of pre-timed
and traffic actuated local controllers without (physical) communication links or master controller
units. TBC can be implemented in all NEMA TS2 and Model Type 170 controllers, and some
TS1 controllers.

Time-Of-Day (TOD) Operation: signal timings plans selected according to the time of day.

Traffic-Responsive Signal Control: the feature of an open or closed loop field master controller
that changes intersection signal timing based on information from system detectors.

Traffic Responsive System: a system in which a master controller either selects or computes
signal timing based on the real-time demands of traffic as sensed by vehicle detectors.

Vehicular Volume: the number of vehicles passing a given point per unit of time.


SOURCES

Traffic Control Systems Handbook – Publication No. FHWA-SA-95-032. U.S. Department of
Transportation/Federal Highway Administration, February 1996

Traffic Engineering Handbook. Institute of Transportation Engineers, 4th edition




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