Analysis of the effect of dual purpose safety cameras at signalised intersections in Adelaide

Abstract

Several signalised intersections in South Australia are equipped with safety cameras which photograph vehicles that either travel though a red signal or exceed the posted speed limit. The registered owners of photographed vehicles are then sent an infringement notice that includes a fine and a number of demerit points. The threat of receiving an infringement is intended to reduce speeding and red signal violations with the aim of reducing the number and severity of crashes at signalised intersections. Infringement data from 21 dual purpose safety cameras at signalised intersections in metropolitan Adelaide was obtained from the South Australia Police. From this data, the change in the number of recorded disobey red light and speeding infringements for each safety camera during the first year of operation was investigated. Red light infringements declined slowly over time while speeding infringements declined rapidly during the first few months and then more gradually thereafter. The decline during the first few months was more rapid for more serious levels of speeding. Theories for these observed changes are suggested and the relationship between infringements and crash rate at signalised intersections is discussed.