Coordination on a Low Budget

1. Coordination on a Low Budget By Ziad A. Sabra Sabra, Wang & Associates, Inc. January 9, 2005

2. Signal TimingProcess

3. Some Observations • Trigger Event • Frequently Politically Sensitive • Data Collection • Not Cheap • Field Adjustments • No Procedure Manual • Dependent on Skills

4. Signal Timing Cost 2.7K to 3.1K 26 to 30 hrs.

5. Why Consider Low Budget Signal Timing • Not sure that we need all of the data • Update signal timing more often • Increase throughput • Improve air quality & fuel consumption • Improve signal timing process

6. Low Budget Signal Timing Sacrifices & Challenges • Signal timing solution may not be optimum • Lacking of Procedural Manual may result in poor practices • Requires expertise in signal timing • Requires good knowledge of Controllers • Could be an iterative process

7. Signal Timing Shortcuts

8. Data Collection Signal Timing Shortcuts • Short-Count Methodology • Node Estimating Methodology Signal Timing • Time-Space Diagram Tools

9. Data Collection • Short Count Options • Count critical intersections only • Estimate secondary intersections • Count all intersections for Xcycles • Count main street only • Count free flow ADT only on approaches and estimate turning movements

10. Signal Timing Cost- One PH Data Collection Only Per Intersection 1.6K to 2K 18 to 22 hrs.

11. Signal Timing Cost- Critical Intersection Only Per System 1.2K to 1.5K 13 to 17 hrs.

12. Pilot Results-Critical Intersection Count Only • Arterial with 5 intersections-3/4 mile • Cycle length 120 seconds • Before Travel Time approx. 3.2 minutes • Avg. three Stops per run • 110 sec. cycle with new splits & offsets • “After” Travel Time approx. 2.2 minutes; (31% reduction) • Avg. < one stop per run • 60 hours to complete; Cost $5,500 ($1100/int.)

13. Signal Timing Shortcuts Signal Timing • Counts are not needed • Interactive Time-Space Diagram Tools • Manipulation of splits and offsets based on field observations • Tools (Synchro, TS/PP-Draft, TSDWIN, etc.)

14. Pilot Results/No TMC • Arterial with 5 intersections-3/4 mile • Cycle length 120 seconds • Before Travel Time approx. 3.20 minutes • Avg. three Stops per run • Same cycle & Splits; New offsets • “After” Travel Time approx. 2.6 minutes (19% reduction) • Avg. one stop per run • 32 hours to complete; Cost $3000 (600/int.)

15. Pilot Results- Time Space Solution • Arterial with 14 intersections-2.15 miles • Cycle length 110 seconds • Before Travel Time approx. 13 minutes • Avg. eight Stops per run • Same cycle & splits but with new offsets • “After” Travel Time approx. 6 minutes; (54% reduction) • Avg. < three stop per run • 40 hours to complete; Cost $4,000 ($300/int.)

16. Low Budget Signal Timing Challenges • Good Knowledge of: • Field Experience with traffic operations and signal timing fine-tuning • Dynamics of traffic operations and queue interaction • Intimate knowledge of the field equipment • Gook skills with signal timing tools (Synchro, PASSER, TRANSYT, TSP-Draft, TSDWIN, etc.)

17. Select Cycle Length • Select Cycle length for Critical intersection

18. Select Splits • Select split to clear side street traffic and pedestrians

19. Offset Selection Challenges • Incorporate Queue Clearance time

20. Offset Selection Challenges • Reduce wasted Green time

21. Offset Selection Challenges • Reduce upstream blocking & consider Lag Left phasing sequence

22. Queue Interaction Strategies & Challenges • Minimize transition between Plans • Minimize disruption to coordination during transition (Shortway, Dwell and Longway)

23. Suggested Future Work • Sensitivity analysis for low budget timing • Estimation for turning movements • More Pilot studies • Procedural Manual