OPERATION OF MERGE JUNCTIONS IN A DYNAMICALLY ENTRAINED AUTOMATED GUIDEWAY SYSTEM

Merge junctions and intersections are the principal capacity limiters and sources of delay in automated guideway transit (agt) networks. The capacity and delay performance of the merge junctions must be thoroughly understood before an agt network can be designed. This paper describes the modeling and simulation of a single merge junction, having two input lanes and one output lane, operating in a quasi-synchronous network. The simulation described here differs from previous merging models by permitting slots to be of variable length to accommodate trains of different lengths, and allowing unlimited maneuvering of trains (if needed). It has the unique ability to represent the operation of a special, newly devised concatenating merge. Which permits trains arriving on separate input lanes to combine themselves into a longer train at the merge. Details of merge operation are demonstrated by sample diagnostic plots, and statistical results (mean values and distribution percentiles) are used to identify performance trends, measured in terms of maneuver distances and slots slipped. Increasing train lengths are shown to require merges to operate at lower traffic intensities, somewhat attenuating the lane capacity advantages produced by long trains. The variable-length, variable-phase slots demonstrate significant performance improvements relative to more conventional fixed-length slots in the simulation results. The concatenating merge is shown to permit use of relatively short maneuver distances even at very high traffic levels. In addition, the effects on merge performance of changes in the incoming train-length distributions, the compressibility of the flow of trains, the merge priority discipline, longitudinal controller performance and the use of fixed-length slots are explained. The paper concludes with a discussion of how the merge performance results can be extended to draw conclusions about performance of agt networks, including full two-way intersections with finite-length maneuver ramps. The trade-off between merge capacity and maneuver ramp length for different incoming train lengths is shown for the two types of merge control which have been modeled (concatenating and isocapacity).(a)

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  • Corporate Authors:

    Pergamon Press, Incorporated

    Headington Hill Hall
    Oxford OX30BW,   England 
  • Authors:
    • Shladover, Steven E
  • Publication Date: 1980-4

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Filing Info

  • Accession Number: 00319074
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD, TRIS
  • Created Date: Sep 16 1980 12:00AM