?How Do Weather Events Impact Roads

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Weather acts through visibility impairments, precipitation, high winds, and temperature extremes to affect driver capabilities, vehicle performance (i.e., traction, stability and maneuverability), pavement friction, roadway infrastructure, crash risk, traffic flow, and agency productivity. The table below, summarizes the impacts of various weather events on roadways, traffic flow, and operational decisions.

Table: Weather Impacts on Roads, Traffic and Operational Decisions

Road Weather Variables	Roadway Impacts	Traffic Flow Impacts	Operational Impacts
Air temperature and humidity	N/A	N/A	Road treatment strategy (e.g., snow and ice control) Construction planning        (e.g., paving and striping)
Wind speed	Visibility distance (due to blowing snow, dust) Lane obstruction (due to wind-blown snow, debris)	Traffic speed Travel time delay Accident risk	Vehicle performance (e.g., stability)        Access control (e.g., restrict vehicle type, close road)        Evacuation decision support
Precipitation  (type, rate, start/end times)	Visibility distance Pavement friction Lane obstruction	Roadway capacity Traffic speed Travel time delay Accident risk	Vehicle performance (e.g., traction) Driver capabilities/behavior Road treatment strategy Traffic signal timing Speed limit control Evacuation decision support Institutional coordination
Fog	Visibility distance	Traffic speed Speed variance Travel time delay Accident risk	Driver capabilities/behavior Road treatment strategy Access control Speed limit control
Pavement temperature	Infrastructure damage	N/A	Road treatment strategy
Pavement condition	Pavement friction Infrastructure damage	Roadway capacity Traffic speed Travel time delay Accident risk	Vehicle performance Driver capabilities/behavior (e.g., route choice) Road treatment strategy Traffic signal timing Speed limit control
Water level	Lane submersion	Traffic speed Travel time delay Accident risk	Access control Evacuation decision support Institutional coordination