Can more rain make the road safer?

Here’s the scoop:

In an analysis of more than 1 million fatal crashes in 48 states, Daniel Eisenberg, a post-doctoral researcher at UC Berkeley’s School of Public Health, was surprised to find that the more it rained or snowed in a month, the fewer deadly traffic accidents there were. Specifically, in any given month, an additional 10 centimeters of rain is linked with a 3.7 percent decrease in the fatal crash rate.

“I had expected to see a positive relationship between the amount of precipitation and the rate of fatal traffic accidents, but my analysis revealed a more complex connection between the two,” said Eisenberg.

He also discovered that the risk of an accident on a rainy day increases with the length of the dry spell preceding it. If there has been rain or snow day after day, the danger due to wet conditions falls.

In other words, if you are used to dangerous roads in recent times, you will drive more carefully. But we are weak, feeble creatures who forget about past dangers all too quickly. Click here for the full story.

The researcher suggests an additional explanation for the phenomenon:

“Oil and debris accumulate on the road when it hasn’t rained for a while, making the roads slicker when it first starts to rain,”

Eisenberg finds another interesting result:

…overall, precipitation had a larger impact on nonfatal traffic accidents.

“For any given day in the state, on average, each centimeter of precipitation increases the risk of fatal crashes by about 1 percent, but for nonfatal crashes, the increased risk is 11 percent,” said Eisenberg.

So, on any given day, rain or snow will lead to increases in nonfatal injury crashes and fender benders much more so than to increases in accidents that involve death.

“People who slow down when the weather is bad may not slow down enough to avoid all crashes, but, on average, they at least reduce the severity of the collision,” said Eisenberg.

In other words, to kill yourself being drunk, very stupid, very unlucky, or a very bad driver are the critical ingredients, not the rain.