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Adaptive Traffic Control Systems: Domestic and Foreign State of Practice (2010) / Chapter Skim
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Pages 28-35

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From page 28...
... . Detection layout used by an ATCS correlates with the adaptive control logic that is used to adjust signal timings for the prevailing traffic conditions.
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From page 29...
... ATCSs that are less sensitive to short-term inputs from detectors tend to be more robust and work better when minor detection failures occur. However, these ATCSs may sometimes be insensitive to the changes in traffic flows.
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From page 30...
... In the past, some of the ATCS deployments in the United States were shut down because of the problems with local traffic controller or central system hardware. Incompatibility of imported local controllers (previously required for operations of some international ATCSs)
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From page 31...
... ATCS Graphical User Interfaces usually provide a full range of operator commands and monitoring functions. Some of the typically displayed data for monitoring operations at an intersection are: • Lamps on/off/flashing • Current phase demands • Detectors occupied • Current cycle time • Operating mode • Alarms • Current phase • Elapsed phase time.
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From page 32...
... Only 17% of the interviewed ATCS users do not believe that reported traffic performance measures are useful for other traffic engineering purposes. ADAPTIVE TRAFFIC CONTROL SYSTEMS AND MICROSIMULATION TOOLS A major disadvantage of field ATCS evaluations, reported through survey response and in the literature, is that these evaluations always require an ATCS to be installed and, as such, they represent post-deployment justification studies.
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From page 33...
... Because real-time control commands are transmitted from the central computer to the local intersection, any interruption in the communications network forces the local controller to operate without that real-time control and revert to its backup plan, which usually is time-based coordination; however, this FIGURE 10 Dynamic map in LA DOT ATCS. ATCS Microsimulation Tool ACS Lite CORSIM, VISSIM BALANCE NONSTOP, VISSIM InSync VISSIM LA ATCS CORSIM (offline post-processing interface)
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From page 34...
... These results can be explained by noting that ATCSs that need central-system-to-field-controller communication require very reliable communication for their ATCS operations, which is ensured through the use of physical media between various elements in their ATCS architecture. According to the survey respondents, a similar share of various media types is observed for peer-to-peer communication Criticality of Communications Between Central System and Local Controllers Percent of Agencies Critically important 62 Somewhat important 15 Not important 23 TABLE 11 COMMUNICATIONS BETWEEN CENTRAL AND LOCAL ENTITIES IN ATCS Twisted Pair; 19; 25% Telephone Line; 20; 26% Fiber Optic; 22; 28% Others; 7; 9% Microwave (terrestrial or satellite)
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From page 35...
... Most of the ATCS users are satisfied with the way their system handles minor detector malfunctions and reports the major detector malfunctions. Early problems with ATCS hardware, which was incompatible for local controllers (primarily for early installations of international ATCSs)
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Key Terms

  • cycle time
  • acs lite
  • queue lengths
  • local controller
  • traffic flow

  • traffic controller
  • adaptive control
  • control logic
  • traffic control
  • traffic data

  • traffic signal
  • adaptive traffic
  • signal status
  • critical intersection
  • timing plan

  • local controllers
  • communications network
  • signal timings
  • traffic network
  • traffic signals

  • local traffic
  • queue length
  • prevailing traffic
  • intersection control
  • fiber optic

  • upstream intersection
  • traffic conditions
  • timing plans
  • signal timing
  • traffic management


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