This report describes the results of a study to investigate the effect of varying the levels of traffic law enforcement on driver behaviour and safety at urban intersections controlled by traffic signals. An assessment of the potential of a traffic violation photorecorder as a means of improving driver behaviour at signalised intersections was also undertaken. Use was made of the traffic conflicts technique and observation of violation incidence to assess any significant changes. The results of the study indicate that the presence of surveillance, whether continuous by mechanical means or sporadic but frequent by patrols, reduces the incidence of unsafe behaviour of drivers. Frequency of visits, not the strength of the patrol, appears to be the main factor. There is no evidence that the duration of stay of a patrol, longer than thirty minutes in one location, is of any additional benefit but as long as surveillance remains evident, its effect on the drivers' behaviour continues. A more intensive study, of much longer duration, would be needed to investigate the influence of increased enforcement on accidents, since a conflict which results in an accident need not necessarily be caused by a violation.
Abstract