An Analysis of Crashes During Winter Weather

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An Analysis of Crashes During Winter Weather

• Tom Maze
• Zach Hans
• Dennis Burkheimer

Mid-Continent Transportation Research
Forum Madison, Wisconsin, August 17, 2006
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Impacts Areas

• Traffic Demand
• Observed Traffic Volumes
• Traffic Flow
• Speed Flow - Density
• Traffic Safety
• Observed crashes during winter weather

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Impacts of Weather on Safety

• Crash rates increase
• For snowfalls gt 0.2 inches/hr crash rates
  increase by 13 times on rural Iowa Interstates
• Changes in crash severity
• ?????
• Changes in crashes throughout the winter
• First snowfall is the most unsafe time of the year

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Crashes Involving Winter Weather Conditions
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Severity of Winter Weather Crashes VS All Winter
Crashes
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Rural Versus Urban Impacts on Primary Highways
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Annual VMT Weighted Snowfall and Winter Weather
Condition Crashes Snowfall Sum(inches x
VMT(nearest) Total State VMT
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Vehicle Characteristics
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Driver Age
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Driver Gender
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Drilling into crash analysis
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Conclusions Continued

• Traffic Safety
• Inclement weather reduces safety
• Snow and ice
• Dramatically increase crash rates
• Crash severity depends on opportunity to drive at
  risky speeds
• Drivers tend to re-learn winter driving skills
• Crash risk is highly dependent on driver
  experience with winter weather
• Over represented in winter crashes
• SUVs, Pickup trucks, and commercial vehicles
• The youngest age group
• Men at any age
• Next year, winter road safety audits