Traffic Signal Timing Report Released
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Our review of the Yellow Light Timing Change and All-Red Clearance Interval Timing Change in Albuquerque, NM focused on determining the traffic safety impact measured by changes in crashes and the cost of crashes.
Among the findings of the study:
- Separate analyses of all 20 study intersections and the 18 YLI intersections was completed.
- The all intersection analyses showed a 7% reduction in total crashes, a reduction in the million entering vehicle (MEV) crash rate, and a weak statistically significant reduction in PDO crashes.
- There was an overall 8.1% reduction in the count of total crashes, a reduction in the MEV crash rate from the pre-study to the post-study time period for the 18 yellow light interval timing change intersections, and a weak statistically significant reduction in the angle crash rate.
- The all intersection cost analysis found a small 11-month total cost increase of $60,000.
- There was no change in the comparison intersection count of crashes or MEV crash rate from the pre-study period to the post-study time period in the average of the crash rates for total, fatal, injury, PDO, rear-end or angle crashes.
- The YLI intersection cost analysis found a small 11-month total cost decrease of $62,800.
- Appropriate yellow light timings are crucial for intersection safety and all red light clearance intervals help reduce the frequency of red-light running and right angle crashes.
- Because the yellow light timing and all-red clearance interval change occurred right at the time the red light camera (RLC) system was discontinued it is not possible to study the change in the yellow light interval timings and all-red clearance interval without including the time period during which the RLC system was operational.
- We were also not able to account for the possible effect of the RLC in the post-time period. There is the possibility that the moderate net cost benefit of the RLC system found in the RLC study extended beyond the end of the program.
- Like RLC systems yellow light time intervals and all-red light clearance intervals are not a complete remedy to address red light running problems that include crashes at intersections. YLI systems and ARL are one of several possible countermeasures that can be utilized to address crash problems at intersections.