Deterrent Effect of Fixed-Site Speed Enforcement in Freeways

Speeding is common in freeways. Speed cameras have limited coverage and the effect of them on speed behavior is unclear. This may lead to irrational decision making on the investment and configuration of enforcement facilities. In this study, required sample speed data were collected in five cross-sections around a speed camera in G45 (Daguang Freeway) of China. Statistics showed that the distance effect model of the speed camera is a concave parabola function. Speeding drivers begin to slow down to speed limits when they approach advance warning signs and then immediately speed up after passing the enforcement site. The deterrent effect of fixed-site speed enforcement is limited to a 300-m range. It was concluded that there is an obvious distance halo effect of fixed-site speed enforcement by deterrence theory. The findings imply that the deterrent effect of fixed-site speed enforcement is weak due to its short effective distance and overt form of control. Reasonable configuration of enforcement facilities and combination with mobile speed enforcement will be appropriate to reduce speeding.