This paper presents the results of an investigation into the levels of acceleration and braking used by drivers at the amber onset of traffic signals. Observations of vehicles on approach to signal controlled junctions were made at three sites in Great Britain (Norwich, Chelmsford and Takeley). A total of about 90 hours of video recordings were made, yielding a total sample of about 3000 vehicles from about 4500 signal cycles. Analysis was carried out using a semi-automated image processing based system. The data used to obtain values of speed and acceleration was the distance of vehicles from the stop line at four known times. (At amber onset, and then at one second intervals up to and including red onset). Response time was assumed to be one second from the amber onset to the start of deceleration. Graphs of the distribution of a) observed acceleration and b) observed braking; c) calculated acceleration and d) calculated braking at each of the three sites are provided. The main points of interest are related to observed acceleration or braking which occurs in inappropriate situations, and raises the question of whether drivers who red run do so out of choice, or are forced to do so because of constraints put upon them by other drivers.
Abstract