Understanding Traffic Signal Warrants and Timing Relationships

Explore the world of traffic signal warrants, basic terminology, and timing relationships with detailed visuals and explanations. Learn about lost time, green indications, effective green time, and flow terminology. Discover concepts like the Change/Clearance Interval and the Dilemma Zone in traffic management. Enhance your knowledge of traffic signal operations and principles through this informative presentation.

• Traffic Signals
• Timing Relationships
• Traffic Management
• Flow Terminology
• Signal Warrants

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Uploaded on Oct 05, 2024 | 0 Views

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1. Signal Warrants

2. Signal Warrants http://mutcd.fhwa.dot.gov/htm/2009r1r2 /part4/part4c.htm Slide 2

3. More Terms

4. Basic Terminology (2/2) Lost time (li) Time lost due to starting and stopping Total lost time (L) Saturation flow Flow at continuous movement assuming always green All-red interval (AR) Time when all signals display red Slide 4

5. More Terminology Display Green (Gi) Time phase diplays green indication Effective green (gi) Time allocated to moving vehicles at saturation flow Total effective green (gT) Green ratio (g/C) Slide 5

6. Timing Relationships Effective green Lost time Lost time Red Green Slide 6

7. Relationships gi = Gi - li + i i = Yi + ARi gT = C - L Slide 7

8. Flow Terminology Discharge headway Time headway for vehicles departing Saturation flow (1,900 pcphgpl under ideal conditions) Slide 8

9. Greenshields Model 4 3 Headway (sec) 2 1 0 1 2 3 4 5 6 7 8 Vehicle Number Slide 9

10. Change/Clearance Interval

11. Change/Clearance Interval Minimum time between the green indications of two phases Yellow + All-red Provide driver with enough time to safely clear the intersection Must be at least 3 seconds Slide 11

12. Dilemma Zone Stop ? Clear For no DZ Distance to stop = Distance to clear Slide 12

13. Dilemma Zone - Time to Clear Stop ? Xo W L Time to clear = (Xo + W + L) / Uo = min Slide 13

14. Dilemma Zone - Time to Stop Xc ? Clear Distance to stop = Xc = Uotr + Uo2 / (2a+64.4G) Slide 14

15. Dilemma Zone Elimination Set Xc = Xo to eliminate dilemma zone Rearrange and solve for min Slide 15

16. Change/Clearance Interval min = tr + [u0 /(2a+64.4G)] + [(W+L)/u0] W is road width to be cleared (ft or m) L is vehicle length (ft or m) u0 is approach speed of vehicles (fps or m/s) tr is driver s reaction time (sec) (1.0 sec) a is deceleration rate (fps2 or m/s2) (10.0 ft/s2) G is percent grade divided by 100 Slide 16

17. Change/Clearance Interval min = tr + [u0 /(2a+64.4G)] + [(W+L)/u0] All Red Yellow Time Slide 17