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Introduction to Traffic Engineering_3_

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					1.4 Basic Concepts in Traffic Engineering
     Mobility versus Accessibility(机动性和可达性)
     Highway Classification (道路分类)
     Uninterrupted (连续流)and Interrupted (间断流)
      flows
     Responsibility and Liability (责任与义务)
     Transportation Legislation (交通立法)
         Mobility versus Accessibility
   Mobility (机动性) --- refers to the ability to travel
    to many different destinations, while
    accessibility (可达性) --- refers to the ability to
    gain entry to a particular site or area


    With an increase of mobility the ability to
    access development decreases, and vise
    versa.
P R O P O R T IO N O F S E R V IC E




                                                   F re ew ay
                  M o b ilit y




                                                   A r t e r ia ls ( M a jo r R o a d )




                                                   C o lle c t o r s ( M in o r R o a d )




          Land A ccess
                                                   L o c a ls (T e rtia ry S tre e t)



F ig u r e 1 .1 R e la tio n s h ip o f
fu n c tio n a lly c la s s ifie d s y s te m in
s e r v ic e tr a ffic m o b ility a n d la n d
Graphic description between mobility and accessibility
                Highway classification

   Location -- urban and suburban (rural)
   Criterion --- specification for roadway design
   Each country has different way in
    determining hierarchy of highways

The purpose of conducting classification for highway is
to clarify the functionality of each category of roadways
in providing services in terms of mobility and accessibility
            China                                  United States
Urban                Rural               Urban                      Rural

Freeway             Freeway              Freeway                   Interstate
Expressway          1st Class Highway
Major Street        2nd Class Highway    Arterials                   Primary
Minor Street        3rd Class Highway    Collector                  Secondary
Tertiary Street      4th Class Highway   Local Street               Tertiary




     With increase of mobility the accessibility will decrease
     Freeway has the highest mobility; whereas local street has the
     highest accessibility
   Freeways or expressways --- access-controlled,
    multilane, divided highways devoted to high-speed,
    long-distance travel with little or no access adjacent
    to land
   Arterials --- roadways serving primarily to move
    traffic between principal traffic generators with
    partially access-controlled (residential access is
    discouraged, but commercial access is allowed),
    there are two categories: major and minor
   Collectors --- roadways serving internal traffic
    movements within an urban area and connecting
    it with the arterial system, there are two
    categories: major and minor
   Local streets --- primarily providing access to
    the development with low-speed
S. AFRICA GENERAL CLASSIFICATION

Primary      Class     Likely Features         Most Likely           Generic
Function      No                               Authorities          Description

                     Long distance
              1.     between cities,             National       Freeways, trunk roads
                     provinces or countries
 Vehicle
                     Relatively long                            Expressways, urban
 Priority     2.     distance between           Provincial      motorways, primary
(mobility)           towns and cities                                arteries

                     Medium distance
                                                                   Arterial roads,
              3.     between districts,        Metropolitan
                                                                 secondary arteries
                     municipalities

  Mixed              Short distance within
              4.                              Local/Municipal      Collector roads
                     districts/suburbs
  Traffic
 (access)            Very short distance
              5.                              Local/Municipal       Local streets
                     (500 m max)

Pedestrian           Suitable for walking,                      Footpaths/cycleways/
              6.     mobility impaired        Local/Municipal    sidewalks, parking
 priority
                     persons and cyclists                         lots, woonerwen
    Uninterrupted and Interrupted flows
   Uninterrupted flow (连续流)facilities have no
    external interruptions (外部干扰) to the traffic
    stream. Pure uninterrupted flow exists mainly
    on freeways and expressways.
   Interrupted flow (间断流) facilities have external
    interruptions to the traffic stream. Almost all
    urban surface streets and highways are
    interrupted flow facilities.
                                       Uninterrupted flow facilities
                                       are fully or partially access-
                                       controlled




Freeway in Germany (2008)




        Expressway in Beijing (2007)
                                          Interrupted flow facilities
                                          are not access-controlled,
                                          with external disruptions,
                                          resulting in stop-and-go




Urban street in Atlantic City, USA




                Urban street in Beijing
           Responsibility and Liability

   Public safety
   Legal obligation --- legal case
   Communication (沟通)with people traffic
    engineers work for --- public hearing (听证会)
    public involvement (公众参与)
   Community protection --- traffic calming (宁静
    交通)
                       Lane reduction is one of
                       traffic calming strategies




Leeds, England




    Dresden, Germany
        Transportation Legislation of USA
   Federal-Aid Highway Act (1916 to 1983) (联邦公
    路法)
   Intermodal Surface Transportation Efficiency Act
    (ISTEA) from 1991 to 1997 (冰茶法案)
   Transportation Equity Act for the 21st Century
    (TEA-21) from 1998 to 2004 (二十一世纪交通法案)
   SAFETEA-LU (Safe, Accountable, Flexible,
    Efficient Transportation Equity Act: A Legacy for
    Users 2005 to 2011)

				
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posted:12/27/2011
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