Headway and Safety Analysis of Speed Law Enforcement Techniques in Highway Work Zones

This paper investigated the headway distribution of platooning vehicles, presence of very short headways (<0.7secnond), and frequency of applying of brakes and changing lane in work zones with and without law enforcement activities. Law enforcement activities include the police patrol car presence (PCP) and automated speed photo-radar enforcement (SPE). Data from two work zones were collected and analyzed. Mean headway of vehicles in work zones increased when SPE or police patrol car presence was utilized in work zones. This is a beneficial effect and indicates that drivers had a longer time to react to the lead vehicles. The law enforcement presence in work zones, either the SPE or police patrol car presence, in general decreased the number of vehicles traveling with a very short headway (<0.7 seconds). The difference in braking behavior was not significant when the SPE case was compared to police car presence. However, lane changing behavior was significantly different for cars traveling in the median lane; also for trucks traveling in the shoulder lane. It is recommended to continue using police car presence or the SPE system to reduce work zone speed and improve traffic flow condition. The use of SPE is recommended particularly in work zones where the lateral space does not allow parking a car on the shoulder (police or violator) or where the traditional law enforcement has limited effectiveness. Future research for modeling the headway distribution of other speed reduction treatments in work zone is recommended.