Assessing the changes in operating traffic stream conditions due to weather conditions

A better understanding of the effects of weather on traffic and more specifically adverse weather events is fundamental for road operations. Recognizing this need advances in sensor technologies enabling real time monitoring of roadways and environmental conditions offer nowadays ways to create better decision support tools for road managers. In this respect a comprehensive analysis of the impact of weather conditions on motorway traffic flow is undertaken. This paper offers a synthesis of four complementary studies, conducted for the assessment of the weather effect on traffic flow and safety. More precisely, this work reports studies that focused on assessing the impact of rain on road traffic operations. An important innovative aspect of this work is that traffic data are recorded (some are individual, others are aggregated) simultaneously with weather and surface data from a road weather information system (RWIS). Then, an in-depth analysis of the effect of weather (rain occurrence) is conducted on the most relevant parameters used for assessing performance of traffic operations and traffic risk characterisation (speed, headway, traffic composition and platooning).