Adverse weather can have a dramatic impact on traffic operations. Motorists drive more cautiously, vehicles cannot start and stop as quickly, and pavement markings and traffic signs can be blocked during a weather event. Such factors can all add up to significantly degraded traffic operations during adverse weather when compared to normal conditions. The purpose of this paper is to identify which traffic parameters in the CORSIM microscopic simulation model are likely affected by adverse weather and to assess which of these parameters most affect the quality of traffic flow. Past research was used to help identify which traffic parameters are affected by adverse weather. Then, a sensitivity test of the numerous freeway car following and lane changing parameters on various congestion levels and roadway configurations was performed to demonstrate which parameters most affect various measures of effectiveness. Overall, this paper presents a planning-level guide to help traffic analysts determine which parameters should likely be changed when modeling weather events. Also, the results from the sensitivity tests show that the Car Following Sensitivity Multiplier and Time to Complete Lane Change parameters are the most sensitive car following and lane changing parameters, respectively, and the ones that produced the most consistent and expected impacts on traffic operations. In addition, the sensitivity study confirms past research that the Mean Free Flow Speed parameter is a crucial parameter to alter when modeling weather events on freeway networks.
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