STUDY OF TRAFFIC FLOW ON A RESTRICTED FACILITY

The objectives of the study were: (1) to investigate the traffic flow on restricted facilities, (2) to develop a model which is capable of describing the traffic on such facilities, and (3) to recommend ways and means of improving the traffic throughout on restricted facilities. The Baltimore Harbor Tunnel was identified as a restricted facility and most of the experimental as well as modeling efforts were focussed on this complex facility. Operational problems were identified in the four subsystems of the tunnel complex namely; (a) the tunnel proper; (b) the ramp area; (c) the merging area; and (d) the queuing area. These areas were studied independently and aggregated in understanding the traffic behavior on the complex. The state space concept (in a mathematical sense) was defined for these subsystems as well as for the entire complex. In order to evaluate different operational strategies, a Markovian model was formulated. This approach which is essentially a probabilistic framework was found to be a very valuable tool in the evaluation of the traffic flow process which is essentially stochastic in nature. Data were collected for a period of four days in the months of February and March of 1973. Conventional regression analysis was employed for the comparison of various theoretical approaches to traffic flow. The queuing area was studied in detail to identify the problems, and operational strategies were formulated for reducing the delay in this subsystem. Experiments were carried out to evaluate these strategies and to compare the cost effectiveness of them. In summary, Phase I of this study has yielded several conclusions, as follows: 1. An automated and accurate data acquisition system is essential to meaningful traffic flow research. 2. The critical bottleneck in the Baltimore Harbor Tunnel complex is located in the region near the foot of the upgrade. This was verified by the development of bottleneck logic. 3. During the peak period, the average concentration goes from a value of about 75 vehicles per mile at the entrance to the tunnel, decreases to a value of about 65 vehicles permile at the bottleneck and then to a value of about 45 vehicles per mile at the tunnel exit. Speed on the other hand shows an average value of about 25 mph at the entrance, increases to a value of about 26 mph at the bottleneck and then downstream to a value of about 33 mph at the tunnel exit. 4. It is possible to obtain an increase of about 15 percent in flow through the bottleneck during the peak period. 5. The operation of the Baltimore Harbor Tunnel toll plaza can be modified to yield substantial reductions in delay to motorists during the off peak hours. The approximate delay ratio is only one-half that of the present operation. 6. A conceptual control framework utilizing a Markov process and dynamic programming approach appears to fit a restricted facility for evaluation of alternative control strategies. 7. Considering only the bottleneck and immediately downstream (on the upgrade) from the bottleneck, control to maintain momentum above a given level will yield not only higher speeds in traversing the upgrade but also higher throughput or flow rates.

  • Supplemental Notes:
    • Prepared for Maryland State Highway Administration in cooperation with U.S. Department of Transportation Federal Highway Administration.
  • Corporate Authors:

    University of Maryland, College Park

    Department of Civil and Environmental Engineering
    College Park, MD  United States  20742
  • Authors:
    • Carter, Everett C
    • PALANISWAMY, S P
  • Publication Date: 1973-6

Media Info

  • Features: Appendices; Figures; References; Tables;
  • Pagination: 244 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00262886
  • Record Type: Publication
  • Report/Paper Numbers: Intrm. Rpt
  • Contract Numbers: AW-72-116-46
  • Files: TRIS
  • Created Date: Nov 20 1974 12:00AM