Docstoc

Traffic Detection Systems

Document Sample
Traffic Detection Systems Powered By Docstoc
					              Traffic Detection Systems
Spring 2007
CEE 320




                                       CEE 320
                                  Steve Muench
              Outline

                        1.   What are traffic detectors?
                        2.   Traffic detector importance
                        3.   Detector types
                        4.   Use Example
Spring 2007
CEE 320
              What Are Traffic Detectors?
Spring 2007
CEE 320
              Traffic Detection Systems Structure


              Detector    Processor/Controller   Storage
Spring 2007
CEE 320
              Why Is Traffic Detection Important?
Spring 2007
CEE 320
              Why Is Traffic Detection Important?
Spring 2007




                             Freeway Monitoring
CEE 320
              Why Is Traffic Detection Important?




                          Actuated Signal Control
Spring 2007
CEE 320
              Why Is Traffic Detection Important?




                                Ramp Meter Control
Spring 2007
CEE 320
              Why Is Traffic Detection Important?




                         Road Discipline Enforcement
Spring 2007
CEE 320
              Why Is Traffic Detection Important?
Spring 2007
CEE 320




                            Dynamic Traffic Assignment
              Why Is Traffic Detection Important?

                        !        !
                                              ATIS




                                                E-Message Sign




                             Control Center

                             Quality Data
Spring 2007
CEE 320
              Traffic Detector Types

              •   Inductive loops
              •   Video
              •   Microwave
              •   Infrared
              •   Acoustic
              •   Radar
              •   Magnetic
              •   Radio frequency
              •   Global positioning system (GPS)
Spring 2007
CEE 320
              Share of Detector Types at new ATMS Sites



                                          Microwave,
                                                       Magnetic,
                                            7.13%
                                                        0.11%
                              Infrared,
                               11.35%                              Loops, 37.75%



               CCTV, 17.03%



                          Acoustic,
                           8.17%
                                          AVI, 3.92%        VIP, 14.55%
Spring 2007
CEE 320
              Popular Traffic Detector Types




                    Inductive loops   Video Image Processors (VIPs)
Spring 2007
CEE 320
              Popular Traffic Detector Types




                                                                                 Remote Traffic
                                                                            Microwave Sensor (RTMS)
Spring 2007
CEE 320




              Photos and picture from Electronic Integrated Systems, Inc.
              Popular Traffic Detector Types




                   Infrared Sensors   Magnetic Sensors
Spring 2007
CEE 320
              Popular Traffic Detector Types
Spring 2007




                         Radio Frequency Tag
CEE 320
              Popular Traffic Detector Types
              ASIM TT 298: Doppler RADAR, ultrasonic, passive infrared.
Spring 2007
CEE 320




              Volume, classification, speed, occupancy, queue detection, wrong-way
              Popular Traffic Detector Types
              ASIM TT 298: Doppler RADAR, ultrasonic, passive infrared.
Spring 2007
CEE 320
              Popular Traffic Detector Types




                   Intersection Control         Traffic Data Acquisition


                             = infrared (counting)

                             = ultrasonic (vehicle height)

                             = microwave doppler radar (speed)
Spring 2007
CEE 320
              Popular Traffic Detector Types




                       GPS-Based Tracking Systems
Spring 2007
CEE 320
              Inductance Loop Detectors

              • Most popular


                                  Photos from Never
                                  Fail Loop Systems, Inc.
Spring 2007
CEE 320
              Inductance Loop Detectors
Spring 2007
CEE 320
              Inductance Loop Detectors

              • A Schematic Diagram




              • The inductance seen at the loop terminals is modified by the
                capacitance and results in an inductance which increases with
                increased operating frequency.
Spring 2007
CEE 320
              Loop Detector Signatures
Spring 2007
CEE 320
              Inductance Loop Detectors

                          Field Component

                                                             Traffic Control
                                                                Cabinet


                                            Pull
                                            Box
                                                   Lead-In
                  Loop                              Cable
                  wires                                           DEUs
Spring 2007
CEE 320
              Inductance Loop Detectors
Spring 2007
CEE 320
              Inductance Loop Detectors
                  Loop inductance decreases when a car is on top of it.
              Inductance
                              T = ton
                       0
                       ton




                              T = toff
                       toff
Spring 2007




                       Time
CEE 320
              Inductance Loop Detectors
                Inductance

               High

               low
                     Tn Single loop measurements?
                            tn1          tn2          tn3     Tn+1   Time

              • Single loops can measure:
                – Occupancy (O): % of time loop is occupied per interval
                – Volume (N): vehicles per interval
Spring 2007
CEE 320
              Dual Loop Detector

              • Formed by two consecutive single loop
                detectors placed a short distance apart




                    lloop        ldist
Spring 2007
CEE 320
              Dual Loop Detectors


                      lloop              ldist

                              T = t2                         T = t1

              • Dual loop measurements
               Speed 
                          l dist                              Speed ot 2  ot1 
                                                 Lvehicle   
                       t 2  t1                                      2
                 oti = on-time for loop detector i
Spring 2007




                Measured vehicle lengths are used to classify vehicles into
CEE 320




                different categories, such as long and short.
              Inductance Loop Detectors
                Only 20 sec aggregated data are available from TSMC




                                  TSMC                    queried
                                 measured data          20 sec data
                                  per 20 sec.      (e.g. 0:00:00 3, 0.98
                                                         0:00:20 2, 0.65)

                              real time
                   Loop      measurements
                   s
Spring 2007




                                         Station               User
CEE 320




                                         cabinet
              Can We Get Speed from a Single Loop?


              • Perhaps…
                                  EVL
                               s
                                   to
                           s = speed (ft/sec)
                        EVL = effective vehicle length (ft)
                           to = occupancy time (s)



                      EVL ~ vehicle length + detector length
Spring 2007
CEE 320
              Can We Get Speed from a Single Loop?

              • Using typical traffic data
                                 N           sec
                           s          3600
                              T O g        hr
                  s = speed (miles/hr)
                  N = number of vehicles in the observation interval
                  T = observation interval (s)
                  O = percentage of time the loop is occupied by vehicles
                      during the observation interval (occupancy)
                  g = speed estimation parameter
                       5280 ft mile
                  g
Spring 2007




                        EVL  100
CEE 320




                                          100 converts percent to decimal
              Inductance Loop Detectors
Spring 2007
CEE 320
              Video Image Processors
Spring 2007
CEE 320
              Video Image Processors
Spring 2007
CEE 320
              A Use Example: Ramp Metering
Spring 2007
CEE 320
              Ramp Meter Schematic




                                        Diagram from
                                     ITS Decision website
Spring 2007
CEE 320
CEE 320
Spring 2007




              Example: SR 520
              What is the Difference?
Spring 2007
CEE 320
              Primary References

              •   Cosgrove, C. and Cutchin, C. (2003). ITS Decision. Website hosted by
                  the California Center for Innovative Transportation at the University of
                  California and Berkeley and Caltrans. http://www.calccit.org/itsdecision

              •   Wang, Y. (2004). CEE 599F, Advanced Traffic Detection Systems
                  Course Pak. Civil and Environmental Engineering, University of
                  Washington.
Spring 2007
CEE 320

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:0
posted:5/21/2013
language:Unknown
pages:42