LOW COST SAFETY IMPROVEMENTS

1. LOW COST SAFETY IMPROVEMENTS Practitioner Workshop The Tools – Traffic Signals – Session #7

2. Traffic Signals Learning Objectives: • Recognize Deficiencies in Operation/Design of Traffic Signals • Select appropriate Enhanced Application Countermeasures for Traffic Signals

3. Traffic Signals Safety Benefits of Signalization: • Traffic Control (3 and 4 approach Stop Controlled - >>>>>> Signal Control) All All 0.86 0.77 * NCHRP 491 “Index of Effectiveness” = AMF

4. Traffic Signals Traffic Signal Countermeasures: 1. Update yellow Clearance timing 2. Add All-Red Clearance phase 3. Improve visibility (12” sections, suppl. heads, etc) 4. Add Back Plates 5. Change Permissive Lefts to Protected Only

5. Traffic Signals Traffic Signal Countermeasures: 6. Add Advance Warning signs with active flashers 7. Add Supplemental Signal Heads 8. Use Overhead Red “T” Heads 9. Change Late Night Yellow/Red Flash to Full Time Signal 10. Coordination of Signals 11. Controller/Actuation Upgrades

6. Traffic Signals Countermeasures: 1. Update Yellow Clearance Interval Yellow Time All-Red Time ITE Traffic Engineering Handbook

7. Traffic Signals Countermeasures: 1. Update Yellow Clearance Interval Yellow Time Red Time ITE Traffic Engineering Handbook CP = t + V/2a + V/20*64.4*g + (W+L)/V • For 85th percentile approach speed of 45 mph, curb radius (Stop bar to curb line of intersecting street of 50’, And Intersection width of 36 feet Yellow Time = t + V/2a + V/20*64.4*g = 1.0 + 45*88/60/2*10 + 45*88/60/20*64.4*0% = 1.0 +66/20 = 1.0 + 3.3 = 4.3 seconds

8. Traffic Signals Countermeasures: • Update Yellow Clearance Interval *TTI, Bonneson, 2003

9. Traffic Signals Countermeasures: 2. Modifying Clearance Intervals * From High Volume Signalized Intersection Handbook

10. Traffic Signals Intersection Countermeasures: 2. Add All-Red Clearance Interval ITE Traffic Engineering Handbook – All-Red Clearance Interval T = ( W + L) / V *Bhesania, 1991 CRF=25% for Add 1.0 Sec Example: 85th Speed=45mph, W=36, curb radius=50’, L=20’ Red Time = (W+L)/V = (50 + 36 + 20)/45*88/60 = 106/66 = 1.61seconds

11. Traffic Signals Countermeasures: • Improve Visibility (12” Indications, Suppl heads) Mast Arm Signals * Iowa CRF = 32% Related Crashes 8” to 12” Indications, *Winston-Salem, NC CRF = 48% Related Crashes

12. Traffic Signals Countermeasures: • Improve Visibility (Mast Arms) Signal Head per lane 22% in Total Crashes 48% in Right Angle Crashes, *Winston-Salem, NC 9% in Fatal & Injury Crashes, British Columbia Supplemental Near Side Supplemental Far Side

13. Traffic Signals 25% to 53% reduction of RLR related Crashes Bonneson, Winston-Salem, NC Countermeasures: 4. Add Back Plates Back Plates No Back Plates

14. Traffic Signals Countermeasures: 4. Add Back Plates Canadian retro- reflectorized backplate 32% reduction in RLR Crashes

15. Traffic Signals Countermeasures: 5. Change Permissive Left to Protected Only -97% Reduction in Left Turning Crashes * Winston-Salem, NC

16. Traffic Signals Countermeasures: 5. Add a Turn Phase to Existing Signal 36% Reduction in Crashes, * Iowa 58% Reduction in Crashes when add Turn Phase and Turn Lane, *Iowa

17. Traffic Signals Countermeasures: 6. Add Advance Warning Sign with Active Flashers Add Signal Ahead Signs, * Winston-Salem, NC 35% to 67% Reduction in RLR Related Crashes, *Bonneson

18. Traffic Signals Countermeasures: • Add Supplemental Signal Head(s) Supplemental Far Left Signal Head

19. Traffic Signals Countermeasures: 8. Use of Overhead RED “T” Signal Heads 35% Reduction in RLR Crashes, *Winston-Salem, NC

20. Traffic Signals Countermeasures: 9. Flashing Operation • Change late night flash of Yellow on mainline/Red on side street to normal operating traffic signal mode

21. Traffic Signals Countermeasures: 10. Signal Coordination 12% Reduction in Peak Hour Crashes - Naperville, IL 25% Reduction in Crashes – San Buenaventura, CA

22. Traffic Signals Countermeasures: 11. Signal Controllers and Actuation

23. Traffic Signals Case Study: Remedy of Naper Blvd & Plank Road Traffic Signal Signal Timing /Coordination and Visibility Improvement Southbound Naper Blvd at Ogden Av toward Plank Road

24. Traffic Signals Case Study : Remedy of Naper Blvd & Plank Road Traffic Signal Signal Timing /Coordination and Visibility Improvement MUTCD Requires 460 feet of visibility Southbound Naper Blvd approaching Plank Road At 450 feet back

25. Traffic Signals Case Study : Remedy of Naper Blvd & Plank Road Traffic Signal Signal Timing /Coordination and Visibility Improvement Southbound Naper Blvd approaching Plank Road At 280 feet back from Stop Bar

26. Traffic Signals Case Study : Remedy of Naper Blvd & Plank Road Traffic Signal • Investigation identified that the county highway agency had made changes in the interconnect system and that the operation of the traffic signal at Plank was no longer coordinated with the signal at a major intersection to the north; coordinated operation was restored.

27. Traffic Signals Case Study : Remedy of Naper Blvd & Plank Road Traffic Signal • Review of the engineering plans identified that the signal design was for tangent approaches; the actual conditions in the field were a reverse 35 mph 6 degree curve. • Signal heads were far side only with 12” sections and backplates

28. Traffic Signals Case Study : Remedy of Naper Blvd & Plank Road Traffic Signal Signal Timing /Coordination and Visibility Improvement Additional Supplemental Near-Side Signal

29. Traffic Signals Case Study : Remedy of Naper Blvd & Plank Road Traffic Signal Signal Timing /Coordination and Visibility Improvement Additional Supplemental Near-Side Signal

30. Traffic Signals Case Study : Remedy of Naper Blvd & Plank Road Traffic Signal Signal Timing /Coordination Visibility Improvement Additional Supplemental Near-Side Signal At 450 feet back from Stop Bar

31. Traffic Signals Case Study : Remedy of Naper Blvd & Plank Road Traffic Signal Signal Timing /Coordination Visibility Improvement Additional Supplemental Near-Side Signal Southbound Naper Blvd at Ogden Av toward Plank Road

32. Traffic Signals Case Study : Remedy of Naper Blvd & Plank Road Traffic Signal Signal Timing /Coordination Visibility Improvement Advance Warning Sign with Yellow Flasher Southbound Naper Blvd approaching Plank Road

33. Traffic Signals Case Study : Remedy of Naper Blvd & Plank Road Traffic Signal Signal Timing /Coordination Visibility Improvement Advance Warning Sign “Be Prepared to Stop” with “When Flashing” Plaque with Flasher tied to Controller Northbound Naper Blvd approaching Plank Road

34. Traffic Signals Questions?