Statistical Investigations of Snowfall and Temperature Interaction with Passenger Car and Truck Traffic on Primary Highways in Canada

Winter weather conditions such as extremely cold temperatures, heavy snowfall, and high wind chills are common occurrences in Canada. Impacts of such adverse weather conditions on total highway traffic volume have been the subject of several research studies in the past. However, none of the past studies investigated thoroughly the impacts of severe cold and heavy snowfall on temporal and spatial variations of truck traffic on Canadian highways. Impacts of weather on route choice behavior of truck and passenger car drivers have also not been addressed in the past. This paper presents an in-depth analysis of the winter weather impacts on classified traffic volume in terms of passenger cars and trucks with considerations of highway types. This study is based on large traffic and weather data sets from weigh-in-motion sites and weather stations in Alberta, Canada. The data were collected from six sites located on two primary highways: Highway 2 and Highway 2A, in Alberta. Winter-weather traffic models were developed using ordinary least-square regression to analyze the truck and passenger car traffic variations with snowfall and temperature. The study results indicate higher reductions for passenger car volumes than truck volumes. The reduction in car and truck traffic volume intensifies with rises in snowfall amount due to cold and snow interactions. Rural long-distance roads (Highway 2) experience higher passenger car volume reductions as compared to truck volume. An important finding for Highway 2A, which is largely a commuter road, is the increase in truck volume during severe winter conditions. This increase in truck traffic is contributed from the traffic shifting from parallel roads with inadequate winter maintenance programs. This paper discusses this unique phenomenon, unlike past studies in the literature.