Road Weather Management Program
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Decision Support, Control and Treatment

About Decision Support, Control and Treatment

In 2000, the FHWA Road Weather Management Program documented the weather information needs of 44 types of transportation managers in order to make 423 kinds of decisions as part of the Surface Transportation Weather Decision Support Requirements (STWDSR) project. By integrating environmental data with other data (e.g., traffic flow data, resource data, population data, topographic data) transportation managers can assess weather impacts on roadways to support their operational decisions. By using timely, accurate, route-specific environmental data in decision-making processes, managers can effectively counter weather-related congestion and delay, reduce weather-related crashes, and disseminate relevant information to travelers. The Maintenance Decision Support System (MDSS) is designed to help winter maintenance managers make road treatment decisions. The Weather Response System (WRS) prototype provides transportation managers with weather forecasts and radar data to support operational decisions.

Some Traffic Management Centers (TMCs) utilize Advanced Traffic Management Systems (ATMS) that integrate environmental data with traffic monitoring and control software. The program has sponsored projects to Integrate Weather into TMC Operations. Traffic managers may access road weather data to make decisions about traffic control and motorists warnings. Control strategies alter the state of roadway devices to permit or restrict traffic flow and regulate roadway capacity. Advanced traffic signal control systems can be used to modifying traffic signal timing based upon pavement conditions. Weather-related signal timing plans modify cycle lengths, splits, and offsets to accommodate changes in driver behavior and decrease arterial delay. Traffic managers can reduce speed limits with Variable Speed Limit (VSL) signs and Dynamic Message Signs (DMS). When travel conditions are unsafe due to flooding, tornadoes, hurricanes, or wild fires, traffic and emergency managers may restrict access to affected bridges, specific lanes, entire road segments, or designated vehicle types (e.g., high-profile vehicles). Ramp gates, lane use control signs, flashing beacons, Highway Advisory Radio (HAR), and DMS are typically employed to alert motorists of weather-related hazards and access restrictions.

Treatment strategies supply resources to roads to minimize or eliminate weather impacts. The most common treatment strategies are application of sand, salt, and anti-icing chemicals to pavements to improve traction and prevent ice bonding. Maintenance vehicles are equipped with plow blades, chemical storage tanks, spray nozzles, and material spreaders to clear roads of snow and ice. The benefits of Anti-icing/Deicing Operations and fixed Anti-icing/Deicing Systems are documented on the Best Practices page. Another type of strategy is conducted by the Utah Department of Transportation (DOT). This agency outfits maintenance vehicles with gas cylinders containing compressed liquid carbon dioxide, which is sprayed into the slipstream of the truck to disperse fog. See the Utah DOT Fog Dispersal Operations case study (PDF, 113K) for more information on this treatment strategy.

Best Practices


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