LADOT’S ADAPTIVE TRAFFIC CONTROL SYSTEM (ATCS)

1. LADOT’S ADAPTIVE TRAFFIC CONTROL SYSTEM (ATCS) Presentation at the TRB Workshop on Adaptive Traffic Signal Control Systems, Sponsored by Signal Systems Committee January 9, 2000

2. GENERAL DESCRIPTION • PC-based real-time adaptive traffic control system • Developed by LADOT staff • Funding provided by City of Los Angeles, LACMTA and FHWA • Window NT with real-time extension • Distributed client-server architecture • Up to 400 intersections and 6400 detectors per system • Currently 237 intersections on-line • Plan to cover 2500 intersections in 3 years

3. WORKSTATION DISPLAY

4. BASIC PHILOSOPHY • Develop an open system to test various control algorithms • Adjust signal timing on a cycle-by-cycle basis: • Cycle Length • Splits (Critical Intersection Control) • Offset (Critical Link Control) • Each Optimizer can function independently • Maximum flexibility in section assignment • Avoid overreacting to short-term variations • Capable of responding to spikes in traffic demand

5. CYCLE LENGTH DISPLAY

6. CONTROL PARAMETERS • Volume and Occupancy, collected every second, but used every cycle • Speed • Detector location • Queue length • Upper and lower limits of cycle length • Phase sequence is fixed • Minimum phase green time

7. DETECTOR DATA • At least one detector per phase • Detectors located 200’-300’ upstream of the intersection • Identify and screen out bad detectors • Smooth calculated demands • Project new cycle lengths • Prorate phase splits based on fixed timing plan when detector data is not available

8. OVERSATURATED CONDITIONS • For isolated intersections • Adapt to high occupancy data with longer cycle length • Adjust splits based on phase demands • For major arterials • Identify critical link(s) and provide progression for the congested approach(s) • Permit double cycling at minor intersections • For networks • Need further research and development

9. TRANSIT PRIORITY • Use loop-transponder technology to detect buses • Check bus schedule in the central database • Provide green extension/red truncation for late buses when needed • Calculate bus arrival time and determine the extension time • Minimize adverse impact on cross streets traffic

10. TRANSIT PRIORITY

11. SYSTEM ARCHITECTURE • Centralized area computers (PC Server) communicate to local controllers. • Multi-port serial cards connect to communication lines. • GUI Client running on area computers and workstations. • Main Data Server provides central traffic data base and coordinates area computers.

13. COMMUNICATION SYSTEM • Dedicated communication path between host and local controllers • Time division multiplexing • Local controllers polled once per second at 1200 bps • Four intersections per communication line. • Multiple communication protocols • Download/Upload to local controllers

14. LOCAL CONTROLLERS • Type 170 controller. • BI Tran Systems 172.3 software. • Type 2070 controller. • City of L.A. Traffic Signal Control Software.

15. CENTRAL HARDWARE REQUIREMENTS • Rack mounted server with a backup PC. • 350 MHz PC with 192 MB RAM • Workstation with two 21-inch monitors. • Multi-port PCI serial cards. • Ethernet network.

16. INSTALLATION COST • Central computer hardware - $40,000 to $50,000 per system • Central software - $1,000 & LADOT license • Local controllers - $8,000-$10,000 per intersection • Loop detectors - $5,000-10,000 per intersection • Communications system - vary by types

17. OPERATIONS AND MAINTENANCE • Central hardware - minimal. • Central software - update costs. • Communications network - labor costs for repair.

18. Verej Janoyan, LADOT (213) 580-5359 e-mail:vjanoyan@dot.ci.la.ca.us Kang Hu, LADOT (213) 485-8523 e-mail:khu@dot.ci.la.ca.us CONTACT PERSONS