Road Weather Management Program
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Best Practices for Road Weather Management Version 2.0


Impact of Weather on Urban Freeway Traffic Flow Characteristics and Facility Capacity


This paper describes how the authors quantified the impact of rain, snow, and pavement surface conditions on freeway traffic flow for the metro freeway region around the Twin Cities. The research database includes four years of traffic data from in-pavement system detectors, weather data over the same period from three Automated Surface Observing System (ASOS) stations, and two years of available weather data from 5 Road Weather Information System (RWIS) stations at the freeway's roadside. Our research classifies weather events by their intensities and identifies how changes in weather type and intensities impact the speed, headways, and capacity of roadways. Results indicate that severe rain, snow, and low visibility cause the most significant reductions in capacities and operating speeds. Rain (more than 0.25 inch/hour), snow (more than 0.5 inch/hour), and low visibility (less than 0.25 mile) showed capacity reductions of 10 to 17 percent,19 to 27 percent, and 12 percent and speed reductions of 4 to 7 percent, 11 to 15 percent, and 10 to 12 percent, respectively.


2005 Mid-Continent Transportation Research Symposium, Iowa State University

Date: 2005


Agarwal, Maze, Souleyrette


Pavement condition
Freeway management
Observing network
Road Weather Information System (RWIS)

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