What is the effect of weather on crash severity? The cross-tabulation below shows how weather is a factor. The yellow cells are just above average, which might not be significant. The red cells are greater than 10% above average, which is probably quite significant if the numbers in the cells are greater than 30. It seems that the big killer on this chart is fog. One theory is that in Alabama, fog is spotty and many drivers just cruise along at high speeds and stumble into the fog. On the other hand, rain is significantly under-represented in the higher severities for the opposite reason, people usually slow down in the rain and very few speed up.
2012-2016 Alabama Integrated Crash Data
For a review of how rain increases crash frequency as well as several other weather-crash details, see: The Effect of Weather on Crashes
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