TRACTION PERFORMANCE OF TRANSIT AND PARATRANSIT VEHICLES DURING WINTER MONTHS

Traction performance of transit and paratransit vehicles during the winter season is an important factor in public transportation system operation. Vehicle traction forces are significantly reduced when travelling on snowy or icy surfaces, specifically during stopping, starting, cornering, and hill climbing. Reduced traction forces result in increased stopping distances and less controllability when a vehicle stops in an emergency situation. In this study, the traction performance of transit and paratransit vehicles was evaluated on snowy and icy surfaces. Field tests were conducted in Fairbanks, Alaska, using three types of vehicles 1) a 41-passenger transit bus; 2) a 32-passenger transit bus, 3) a 9-passenger paratransit vehicle. Each vehicle was tested for different combinations of tire types that included highway tires, snow tires, studded-siped tires, highway 3-rib tires, all-season tires, and snow siped tires. Winter traction performance was evaluated using a number of tests that included stopping distance, starting traction, hill-climbing, cornering, and controllability. Results indicate that winter traction performance is significantly influenced by vehicle type, tire combinations that are most suitable for winter traction are presented.