Anyone who uses surface transportation has been affected by delays caused by various forms of weather. Whether it is rain or snow, ice or fog, the result is usually the same. Travel delay rises as traffic congestion increases. The Federal Highway Administration's (FHWA) Road Weather Management Program (RWMP) has been sponsoring research into the impacts of weather on surface transportation. One specific research task involved attempting to quantify the amount of travel delay imposed upon drivers due to the effects of inclement weather. This paper describes two different methods used to approximate the average travel delay impacts of weather along approximately 712 directional miles of roadway around metropolitan Washington, D.C based on weather and travel time data spanning from December 1999 to May 2001. Each method uses meteorological data sets of differing temporal and spatial resolutions in conjunction with travel time data archived from a real-time publicly available internet-based travel advisory source. The average increase in travel time due to precipitation for peak-period traffic in the Washington DC region is estimated to be 25% based on radar data specific to particular roadways. The less refined analysis based on regional measurements of weather suggest a 12% increase in travel time due to factors of precipitation, visibility, and wind. During the off-peak periods in the daytime, travel time increases by approximately 13% due to the array of weather attributes. Measuring the impact of only precipitation, suggests that during the off-peak periods, precipitation causes a 3.5% increase in travel time. This estimate, however, is likely to be lower than reality due to the limitations in travel time data.
Abstract