1. Signal Timing: Putting it All Together

2. Steps in Designing a Traffic Signal Timing Plan (1/2)
1. Determine lane configurations and lane volumes
2. Propose Phase Plans (provide diagrams)
3. Critical Volumes for each phase (for each proposed plan)
4. Recommend phase plan
5. Clearance Intervals

3. Steps in Designing a Traffic Signal Timing Plan (2/2)
6. Lost Time
7. Cycle length
8. Green Splits
9. Display Greens
10. Provide Final Timing Diagram
Repeat as needed for other lane configurations.

4. Critical Concepts to Note
Shared LT+TH lanes
Use of left turn equivalents for lane volume allocation
LT phase impact on critical lane volumes
Overlapping phasing: exception to the highest volume is critical rule
Every intersection is different in terms of which phase plan works best

5. Full Example Speed = 40 mph tr= 1 s s=1850 vphpgpl a=10 ft/s2
start and end loss = 3 s
11 foot lanes
24 foot vehicles

6. Steps in Designing a Traffic Signal Timing Plan
1. Determine lane configurations and lane volumes
2. Propose Phase Plans (provide diagrams)
3. Critical Volumes for each phase (for each proposed plan)
4. Recommend phase plan
5. Clearance Intervals

7. Full Example 480 200 NB & SB Exclusive LT lane
390
650
480
200
NB & SB
Exclusive LT lane
Single shared TH & RT lane

8. Full Example 480 200 WB 1. Opposing traffic to LT EB TH+RT=200+200=400
390
650
480
200 WB
1. Opposing traffic to LT
EB TH+RT= =400
2. 1 LT =2 TH
3. Total equivalent TH
300+2(100)+150 = 650
4. Per lane 650/2 = 325
325
225
125
100

9. Full Example 480 200 EB 1. Opposing traffic to LT WB TH+RT=300+150=450
390
650
480
200 EB
1. Opposing traffic to LT
WB TH+RT= =450
2. 1 LT =2 TH
3. Total equivalent TH
200+2(50)+200 = 500
4. Per lane 500/2 = 250
325
225
125
100
250
200
150 50

10. Steps in Designing a Traffic Signal Timing Plan
1. Determine lane configurations and lane volumes
2. Propose Phase Plans (provide diagrams)
3. Critical Volumes for each phase (for each proposed plan)
4. Recommend phase plan
5. Clearance Intervals

11. Phase Plans for EB/WB

12. Steps in Designing a Traffic Signal Timing Plan
1. Determine lane configurations and lane volumes
2. Propose Phase Plans (provide diagrams)
3. Critical Volumes for each phase (for each proposed plan)
4. Recommend phase plan
5. Clearance Intervals

13. T Phase Plans for EB/WB Max {(325+50),(250+100)} = 375 228 280 Σ = 508
Note: Unopposed LT, new lane volumes EB
Total equivalent TH
(50)+200 = 455 or 228/lane WB
(100)+150 = 560 or 280/lane
Σ = 508

14. Steps in Designing a Traffic Signal Timing Plan
1. Determine lane configurations and lane volumes
2. Propose Phase Plans (provide diagrams)
3. Critical Volumes for each phase (for each proposed plan)
4. Recommend phase plan
5. Clearance Intervals

15. Phase Plans for NB / SB

16. Steps in Designing a Traffic Signal Timing Plan
1. Determine lane configurations and lane volumes
2. Propose Phase Plans (provide diagrams)
3. Critical Volumes for each phase (for each proposed plan)
4. Recommend phase plan
5. Clearance Intervals

17. T Phase Plans for NB / SB Max {(480+390), Min {200,390}
( )} = 870
Min {200,390} T
190 ( )
Max {390,200}
Max {480,460}
Max {650,480}
ΣCV = 870
ΣCV = 1040

18. Steps in Designing a Traffic Signal Timing Plan
1. Determine lane configurations and lane volumes
2. Propose Phase Plans (provide diagrams)
3. Critical Volumes for each phase (for each proposed plan)
4. Recommend phase plan
5. Clearance Intervals

19. Steps in Designing a Traffic Signal Timing Plan
1. Determine lane configurations and lane volumes
2. Propose Phase Plans (provide diagrams)
3. Critical Volumes for each phase (for each proposed plan)
4. Recommend phase plan
5. Clearance Intervals

20. EB/WB Clearance Interval
τ1 = tr + [u0 /(2a)] + [(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 (f/s or m/s) =
tr is driver’s reaction time (sec) =
a is deceleration rate (ft/s2 or m/s2) =

21. Steps in Designing a Traffic Signal Timing Plan
6. Lost Time
7. Cycle length
8. Green Splits
9. Display Greens
10. Provide Final Timing Diagram
Repeat as needed for other lane configurations.

22. Lost Time
L = start/end loss + AR

23. Steps in Designing a Traffic Signal Timing Plan
6. Lost Time
7. Cycle length
8. Green Splits
9. Display Greens
10. Provide Final Timing Diagram
Repeat as needed for other lane configurations.

24. Optimum Cycle Length
1.5 L + 5
Co = =
1- S yi

25. Steps in Designing a Traffic Signal Timing Plan
6. Lost Time
7. Cycle length
8. Green Splits
9. Display Greens
10. Provide Final Timing Diagram
Repeat as needed for other lane configurations.

26. Green Splits
CV CV2 870
gT = C - L
gi = gT (yi / Y)

27. Steps in Designing a Traffic Signal Timing Plan
6. Lost Time
7. Cycle length
8. Green Splits
9. Display Greens
10. Provide Final Timing Diagram
Repeat as needed for other lane configurations.

28. Display Greens Gi = gi + li - τi
G1 = (3+0.6) = 12.3 seconds
G2 = (3+0.8) = 29.3 seconds

29. Steps in Designing a Traffic Signal Timing Plan
6. Lost Time
7. Cycle length
8. Green Splits
9. Display Greens
10. Provide Final Timing Diagram
Repeat as needed for other lane configurations.

30. Timing Diagram
12.3
15.8
50.0
16.4
45.7
49.2
50.0