Causes of Weather-Related Crashes in Salt Lake County, Utah

In 2010, the World Health Organization declared 2011 to 2020 the Decade of Action for Road Safety in response to the enormous toll that roadway crashes take on individuals, communities, and national economies. More than 6.2 million vehicle crashes occurred in the United States in 2015, resulting in around 2.4 million injuries and more than 35,000 fatalities. Motor vehicle crashes in the United States in 2015 had an economic cost of $836 billion, equal to nearly 5 percent of the U.S. gross domestic product. For this study, more than 122,000 crashes occurring in Salt Lake County, Utah, from 2012 to 2016 were analyzed to see how weather conditions affected the number and type of crashes observed. Approximately 12 percent of crashes occurred under "adverse weather conditions." Weather-related crashes were most likely in the winter season and were very highly correlated with monthly snowfall. Although the greatest number of crashes occurred during evening rush hours, adverse weather-related crashes made up a larger percentage of crashes from 5 to 7 a.m. Although excessive speed was much more likely to be a factor in crashes during adverse weather, such crashes, on average, were less severe. Roadway slope also played a significant role, with slight increases causing more crashes.