Additional Dilemma Zone Protection for Trucks at High-Speed Signalized Intersections

Trucks are typically overrepresented in rural intersection crashes. These heavy vehicles have different stopping characteristics from the passenger cars around them, and such differences can result in conflicts and crashes. Crashes between trucks and passenger cars may be particularly severe. Trucks may require 50% more distance to stop than passenger cars, so they probably have a different dilemma zone than passenger cars. In addition, truck drivers may be less willing to stop for a red signal, and trucks are about twice as likely as passenger cars to run red lights. This paper presents the concept of providing additional dilemma zone protection for trucks by allowing for the additional time and distance that trucks require to stop and thereby reducing the number of trucks in the dilemma zone and red light violations. The concept was tested by using the detection control system developed at the Texas Transportation Institute. The use of a truck dilemma zone 1.5 s longer than the passenger car dilemma zone produced a 47% reduction in the number of trucks in the dilemma zone without a noticeable effect on intersection delay.