AgdaPkt 2010-10-25 - Laserfiche WebLink

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� 7.B Pa e 5 undocumented accidents in particular have dropped although the Department has the �east amount of data to analyze, as these were merely called in to the Department with no report , generated. ' Yellow Light Intervai Timing There has been some recent discussion among cities that are using automated red light photo enforcement systems regarding the extension of the yellow light interval of traffic signals and its potential impact on both �iolations and overall traffic safety. The minimum j interval time for yellow lights is established by the California Manual on Uniform Traffrc ' Control Devices (MUTCD) and the California Vehicle Code. The MUTCD states tha# the � yellow interval should have a duration befween three and six seconds. The City tra�c , engineering staff is responsible for setting and maintaining the traffic signal phase times for ', the intersection of Veterans Blvd. and Whipple Ave. The table below from the California ', MUTDC lists #he recommended minimum yellow interval based on posted speed limit. ', �, Posted or Prima Facis S eed Minimum 1��ttaw Int�erval m h Seconds 25 or less 3.� 30 3.2 35 3.6 40 3.9 45 4. 3 The intervals are established based on a"comfortable" deceleration rate of 10 ftlsec/sec. They account for potential wet pavement and are easily achievable for large vehicles that do not stop very well. For both southbound Veterans Blvd. and eastbound Whipple Ave., the yellow interval is currently set for 4.0 seconds. There is also a red clearance (all red, all directions simultaneously) set at one second for both approaches. Combined, this effectively provides a 5.0 second clearance interval for each approach. For Veterans Blvd., the minimum yellow interval would be 3.6 seconds based on its 35 mph limit; and for Whipple Ave., the minimum yellow interval would be 3.0 seconds based on the 25 mph speed limit. In each case, the yellow interval is longer than the minimum prescribed time. Per the traffic engineering staff, the determination of the yellow clearance intervals requires engineering judgment and is based on vehicle speeds, intersection geometry, and other considerations. The presence or absence of automated photo red light system should have no bearing on this analysis. Unnecessarily long yellow times may encourage drivers to use it as part of the green interval and excessively long yellow and all-red intervals result in inefficient signal operations. This is particularly important at a hea�ily travelled intersection such Whipple and Veterans. Additional(y, excessively long yellow intervals may also cause more "rear end" collisions because drivers who are accustomed to the "normal" yellow interval may want to s#op, while the driver behind may know that there is a longer interval and try to proceed against it. Accordingly, the traffic engineering staff believes the yellow intervals as currently set are safe, efficient, and proper, and should not be lengthened. 5