Speed Selection During Winter Road Conditions
The unpredictability of weather conditions may have direct or indirect impacts on traffic operations and driver behaviors (e.g. speed, headway, and gap). The impacts may occur during or after the weather events, be of short- or long-term duration, and include direct and indirect effects. Adverse winter storms, flooding, or hurricanes may cause major delays in traffic operations and cost millions of dollars (FHWA, 2006). The rain, fog, and snow can result in serious impacts on roadway systems and well-being of the road users. About 24 percent of all reported motor vehicle crashes in the United States are related to weather conditions. They result in more than 673,000 injuries and about 7,400 fatalities per year (Pisano, et al., 2009).
A study of crash rates along Wyoming I-80 corridor was conducted by the University of Wyoming in 2006 (Tomasini, 2006) indicated that the segments between Laramie and Rawlins had the highest crash rates for the years 1995 to 2005 due to high wind, blowing snow, and icy road surface conditions. Road closure is one potential measure to mitigate adverse weather conditions’ however other solutions are also necessary. Recent studies showed that average road closure time between Laramie and Rawlins was eight hours per closure resulting in a conservative estimate of economic impact of about $8–$12 million in delay costs per one road closure (Young & Liesman, 2007). Another study found that crashes during winter are 2.82 times higher than the number of summer crashes (Young, et al., 2012). Therefore, better understanding of adverse weather condition might be helpful to reduce crashes and improve safety on traffic operations.