Methods of traffic signal control and signal timings at high speed sites

When traffic signals change from green, drivers decide whether they can safely stop or continue and clear the stop line before the start of red. Close to, and far from, the junction the decision is relatively easy, but not at interim distances where the probability of accidents is highest, called the dilemma zone. It is desirable to minimise the dilemma zone, as this should reduce the number of drivers having to make a difficult decision when the traffic signals change. This paper examines the results from two sets of surveys. The first investigated how different signal control strategies affected driver reactions and the dilemma zone. The second used a simulator to introduce new signal timings and advanced warning to drivers.