IMPROVED CONTROL LOGIC FOR USE WITH COMPUTER-CONTROLLED TRAFFIC

This report documents research in which the ASCOT (Adaptive Signal Control Optimization Techniques) software system for computer control and surveillance of traffic was formulated, developed, installed in an operational computer traffic control facility in the City of San Jose, California, and evaluated by on-street measurement and computer simulation. The ASCOT system includes on-line signal timing plan computation, cycle-to-cycle variable split controls, and cycle-length and offset adjustment coupled with phase extension at congested intersections. With only the variable split and congested intersection controls enabled, ASCOT's ability to reduce vehicle travel time in non-trivial street networks was found to be comparable or superior to what could be achieved by intensive traffic engineering efforts using the SIGOP and TRANSYT methods. In this mode, ASCOT has been used operationally in San Jose for more than two years. Two complementary approaches to real-time offset computation were developed and tested. Both showed promise but neither producted demonstrably optimal sets of offsets. Preliminary tests of ASCOT's sensitivity to level of detectorization were made. The ASCOT development has demonstrated that very flexible modes of traffic control can be achieved using low-cost miniclass computers.

• Supplemental Notes:
  • Prepared for Transportation Research Board, National Cooperative Highway Research Program, Washington, D.C.
• Corporate Authors:

  Stanford Research Institute

  333 Ravenswood Avenue
  Menlo Park, CA  United States  94025
• Authors:
  • Ross, D W
  • Humphrey, T L
  • Mahoney, E E
  • Sandys, R C
  • Williams, Gregory L
  • Wohnoutka, R
  • Wong, P J
  • Zeidler, H M
• Publication Date: 1977-6

Media Info

• Features: Appendices; Figures; Tables;
• Pagination: 353 p.

Subject/Index Terms

• TRT Terms: Computers; Minicomputers; Offsets (Traffic signal timing); Real time control; Signalized intersections; Software; Traffic signal controllers; Traffic signal cycle; Traffic surveillance; Travel time
• Old TRIS Terms: Low costs; Real-time systems
• Subject Areas: Highways; Operations and Traffic Management;

Filing Info

• Accession Number: 00158153
• Record Type: Publication
• Report/Paper Numbers: NCHRP Proj. 3-18(1) Final Rpt.
• Contract Numbers: HR3-18(1)7 3-18(1)/1
• Files: TRIS
• Created Date: Sep 28 1977 12:00AM