Calibrating VISSIM to Adverse Weather Conditions

Calibrated simulation models taking into account adverse weather conditions can be used to optimize traffic management measures, such as intersection signals for conditions. With snowy conditions, for example, motion of vehicles changes because drivers tend to accelerate more slowly, increase distance and drive with lower speeds. Such changes become observable for lower saturation rates at intersections. In order to simulate traffic in adverse conditions in a valid way, the parameters of a simulation have to be calibrated. This paper identifies the most important parameters of the VISSIM simulation program that are sensitive to snowy road conditions and indicates valid parameter subspaces leading to a good match of the simulation model with observed saturation flow rates. Keywords: Microscopic traffic model, calibration, saturation flow rate, start up delay