Analysis of Weather Impact on Travel Speed and Travel Time Reliability

Weather conditions may have significant impact on traffic flow. Under adverse weather, traffic speed reduces and congestion emerges. The joint effects of adverse weather and recurring traffic congestion throughout the day may lead to more unpredictable travel time. The objective of this study is to examine the impact of adverse weather on traffic speed and travel time reliability in various highways. Weather data collected from Road Weather Information System (RWIS) Environmental Sensor Stations (ESS) and speed data collected by INRIX are applied. Data for various highway classifications and different time periods are selected to conduct the comparative analysis. Travel time reliability is measured by the buffer index. It was found that adverse weather reduces traffic speed and leads to less travel time reliability. The extent of influence varies with precipitation intensity. The results may assist transportation agencies for traffic management and travelers for trip planning under adverse weather.