Effects of reduced threshold of automated speed enforcement on speed and safety

This study was designed to evaluate the effects of a reduced threshold of the fixed automated speed enforcement system on speed and safety on a two-lane rural road. The threshold was lowered from 20 km/h to 4 km/h and the public was informed about the change. Driving speeds on the experimental and control road before and after the change were compared. The main results showed that the reduced threshold decreased the mean speed by 2.5 km/h, the standard deviation of speed by 1.1 km/h and the proportion of exceeding vehicles by 11.8 percentage units. In conclusion, lowering the threshold of automated speed enforcement combined with an appropriate information campaign bring about a significant speed reduction that could contribute to substantial safety benefits.