McClanahan's Red Light Running Solution

E. Thomas McClanahan, conservative pundit of the Kansas City Star, in a commentary of January 4, 2009, stated that "Longer yellow-light times mean fewer violations and accidents." In addition to the "blinking green" and "point of no return striping" he has offered yet another idea as to how the problem of motorists disrespecting red lights can be solved. McClanahan cites several studies that reported decreases in intersection accidents after yellow-light times were lengthened, but he did not mention the duration of the previous yellow-light phase of the traffic signal cycle, the speed limit applicable at the intersection, the type of collision reduced, or any other of several factors that could affect the number of collisions. In other words, he focused solely on the length of the yellow-light phase of the signal cycle as the determinant of motoring safety.

The KC Star editorial board stated recently that the yellow-light duration at intersections where cameras are planned ranged from 3.6 seconds to 3.9 seconds and, that where cameras are installed, they would monitor the times to see if they are changed or not. Considering all the interest in the fairness and practicality of red-light cameras, it is time to look at some facts. At 35 miles per hour, the speed limit usually applicable on streets with traffic signals, a vehicle will travel 180 feet in 3.5 seconds or 205 feet in 4.0 seconds. According to national traffic authorities, the stopping distance for a car traveling 35 mph, assuming good brakes and a good road surface condition, is approximately 51 feet. From this data, it can be seen that a vehicle driver, who is not speeding excessively or is not physically impaired, has more than sufficient reaction time and braking power to bring a vehicle to a stop before entering an intersection.

A short ( one to two second) yellow light phase can present problems to speeding drivers, while longer phases (three to four seconds) are more forgiving of excessive speed. Lengthening a short yellow phase could be beneficial, but doing the same for a yellow phase that is already of ample duration would be unlikely to provide any benefit.

Personally, I consider red-light cameras to be a "two-fer", better traffic enforcement and more revenue, both of which Kansas City surely needs. If McClanahan really wants to "step up enforcement in the proper way-- with traffic cops issuing tickets at the scene", then I'll be looking for his commentary supporting a tax increase to pay the bill for his desire.