Yellow Light Timing

Ever since John’s little flapdoodle over the introduction of red light cameras, I’ve been keeping a stopwatch in my car and measuring the yellow light periods. As Ham noted, Holly Street in Bellingham seems dangerous because of the short yellows. Now the results are in, I can say that Holly and Magnolia Streets have the shortest yellow periods I’ve found: they are three seconds or slightly less. Every other yellow I’ve timed has been three and three quarters to four seconds. All of the traffic lights controlled by the Washington Department of Transportation (those at freeway on and off ramps) are yellow for four seconds. Lights in the county (on Meridian and Hannegan) and in beautiful downtown Ferndale are over three and a half seconds with several measuring about four seconds.

The traffic standards organizations recommend that no traffic light be yellow for less than three seconds where the speed limit is 25 mph and four or five seconds minimum when the speeds are faster.

The lights in downtown Bellingham are a mystery. Trying to drive at the speed limit with the lights in sequence has always been frustrating. If traffic is slow, it’s possible to hit every single light as a red. I always have the feeling that the yellow time is too short and now I know it’s true.

The intersections at State and Railroad are wide enough that three seconds is frequently not long enough to leave the intersection before the light turns red. Twice I’ve timed the lights going west on Holly at Railroad and had the light turn yellow as I was entering the intersection and red before I left it.

Studies by traffic safety organizations have shown that accidents are frequently caused by too little time on the yellow cycle. Some studies have shown that increasing the yellow period by one second reduces accidents by 30%.

The clincher for me was the fact that the yellows on Holly and Magnolia are too fast to clear the intersection before the light went red under normal traffic densities. The city needs to fix this.