Effects of Work Zone Presence on Injury and Non-Injury Crashes

Work zones in the US have approximately 700 traffic-related fatalities, 2,400 injury crashes and 52,000 non-injury crashes every year. Due to future highway reconstruction needs, work zones are likely to increase in number, duration and length. This study focuses on work zone length mainly due to its policy-sensitivity. A unique data set of California work zones was created, including crash data, road inventory data and work zone related data. Crash rates and frequencies were calculated for pre-work zone and during-work zone periods. For the freeway work zones investigates, the total crash rate for the during-work zone period was 21.5% higher (0.79 crashes per million vehicle km) than the pre-work zone period (0.65 crashes per million vehicle km). Compared to the pre-work zone period, the increase in non-injury and injury crash rates were 23.8% and 17.3% respectively. Next, crash frequencies were investigated using negative binomial models, which showed that frequencies increased with increasing work zone duration, length and average daily traffic. Most importantly, after accounting for various factors, longer work zone duration significantly increases both injury and non-injury crashes.