Rain-which occurs moreįrequently than snow, ice, and fog-leads to greater delay. This amounts to an estimatedĥ44 million vehicle-hours of delay per year.
#Big weather events 2016 driver#
(Sources: " Highway Capacity ManualĢ000" Chapter 22, " Capacity-Reducing Occurrences", " Driver Maximum flow rates can decline by 14 percent in heavy rain and by 30 toĤ4 percent in heavy snow. Light snow can decrease flow rates by 5 to 10 percent. Light rain can decrease freeway capacityīy 4 to 11 and heavy rain can cause capacity reductions of 10 to 30 percent.Ĭapacity can be reduced by 12 to 27 percent in heavy snow and by 12 percent Speed varianceĬan fall by 25 percent during rain. Snow can cause free-flow speed to decrease by 5 to 64 percent. Free-flow speed can be reducedīy 2 to 13 percent in light rain and by 6 to 17 percent in heavy rain. Low visibility canĬause speed reductions of 10 to 12 percent. In heavy snow,Īverage freeway speeds can decline by 5 to 40 percent. Heavy rain can decrease average speed by 3 to 16 percent. On freeways, light rain or snow can reduce average speed by 3 to 13 percent.(Sources: " Weather Impacts on Arterial Traffic Flow (PDF 92KB)" and " Weather-Responsive Time delay on arterials can increase by 11 to 50 percent and start-up delayĬan increase by 5 to 50 percent depending on severity of the weather event. Saturation flow rate reductions can range from 2 to 21 percent. Average arterial traffic volumes can decreaseīy 15 to 30 percent depending on road weather conditions and time of day. On signalized arterial routes, speed reductionsĬan range from 10 to 25 percent on wet pavement and from 30 to 40 percent Weather events can reduce arterial mobility and reduce the effectiveness.(e.g., large trucks in high winds) also decrease roadway capacity. Road closures and access restrictions due to hazardous conditions Capacity reductions can be caused by lane submersion due to floodingĪnd by lane obstruction due to snow accumulation and wind-blown debris.(Source: Ten-year averages from 2007 to 2016 analyzed by Booz Allen Hamilton, based on NHTSA data). That is on an annual basis, nearly 4,900 fatal crashes, over 301,100 injury crashes and nearly 919,700 PDO crashes occur in adverse weather or on slick pavement. By crash type (not shown in above table) for an average year, roughly 15% of fatal crashes, 19% of injury crashes, and 22% of property-damage-only (PDO) crashes occur in the presence of adverse weather and/or slick pavement.Table: Weather-Related Crash Statistics (Annual Averages) A much smaller percentage of weather-related crashes occur during winter conditions: 18% during snow or sleet, 13% occur on icy pavement and 16% of weather-related crashes take place on snowy or slushy pavement. The vast majority of most weather-related crashes happen on wet pavement and during rainfall: 70% on wet pavement and 46% during rainfall.On average, nearly 5,000 people are killed and over 418,000 people are injured in weather-related crashes each year. Weather-related crashes are defined as those crashes that occur in adverse weather (i.e., rain, sleet, snow, fog, severe crosswinds, or blowing snow/sand/debris) or on slick pavement (i.e., wet pavement, snowy/slushy pavement, or icy pavement). Approximately 21% of these crashes - nearly 1,235,000 - are weather-related. On average, there are over 5,891,000 vehicle crashes each year.Driver capabilities/behavior (e.g., route choice).
Access control (e.g., restrict vehicle type, close road).Lane obstruction (due to wind-blown snow, debris).Visibility distance (due to blowing snow, dust).Road treatment strategy (e.g., snow and ice control).Table: Weather Impacts on Roads, Traffic and Operational Decisions The tableīelow, summarizes the impacts of various weather events on roadways, traffic Infrastructure, crash risk, traffic flow, and agency productivity. (i.e., traction, stability and maneuverability), pavement friction, roadway Weather acts through visibility impairments, precipitation, high winds,Īnd temperature extremes to affect driver capabilities, vehicle performance
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