Evaluation of Kentucky’s Work Zone Speed Camera Pilot Program

Kentucky introduced automated speed enforcement in work zones to mitigate hazards and improve the safety of motorists and workers. This study describes the impacts of automated speed enforcement at five pilot sites. Researchers analyzed speed data and crash data from pilot sites and paired control sites. The control sites and pilot sites had similar traffic volumes, lane configurations, and functional classifications. Analysis drew on over 15 million individual speed records captured using automated enforcement cameras as well as segment-level speed data from HERE. Active enforcement at pilot sites was associated with lower mean, 85th-percentile, and 99th-percentile vehicle speeds. Average vehicle speeds were 1.0–7.5 mph lower during active enforcement, and fewer vehicles exceeded work zone speed limits. The percentage of vehicles traveling more than 10 mph over the speed limit fell 6–23% during active enforcement. Because motorists also slowed down in work zones at control sites, not all speed reductions observed at pilot sites can be attributed to automated enforcement. After adjusting for differences in speed at control sites during periods of active and inactive enforcement, the net effects of enforcement were modestly positive at interstate pilot sites, but there were no clear reductions in speed on the urban arterial and rural highway included in the study. Due to the short duration of automated enforcement activities, researchers had to rely on naive crash analysis to evaluate safety impacts. This found that at most sites the total number of injury crashes fell following camera deployment, although injuries skewed more severe. Speeding-related crashes were exceedingly uncommon at pilot sites (both before and after camera deployment) and control sites. Overall, the study supports using automated speed enforcement to improve work zone safety, particularly given its effectiveness in reducing 85th- and 99th-percentile speeds (i.e., high-risk speeding).