Over the past several winters, the nation has seen a number of multi-car wrecks during winter weather events with modest total snow accumulations, but with snow that falls quickly. The 50-vehicle pileup in Michigan that shut down part of U.S. Highway 131 near Grand Rapids a few weeks before Christmas 2015 was one such case.
"There seems to be a critical time of accumulations first occurring on untreated roads with some drivers not yet realizing the roads have become slick, maintaining their near-normal speeds until a slideoff or wreck occurs," said weather.com senior meteorologist Jonathan Erdman.
From 2004 to 2013, nearly a quarter of all traffic crashes in the U.S. were caused by weather, according to 10-year averages released by the National Highway Traffic Safety Administration. Of those, 17 percent occurred during snow or sleet, 13 percent on icy pavement and 14 percent on snowy or slushy pavement.
Walker Ashley, associate professor of meteorology at Northern Illinois University, contends that "minor" winter events are more deadly (on Midwestern roads, at least) than notable winter storms due to heavier traffic on roads and possibly more dangerous road and visibility conditions than perceived by drivers.
It's our perception of these light or sudden snow and ice events that gets us in trouble, says University of Wisconsin-Whitewater professor of psychology David Havas.
People's brains need to adapt each year to winter driving, Havas told the Milwaukee Journal Sentinel in 2014, and, "very often, the world changes faster than the brain learns, creating a learning lag." Drivers' brains just haven't had time to fully process the reality of what their eyes are telling them.
It's easy to make the decision to slow down, or even stay off roads buried in a foot of snow, or shiny with accumulated ice, but it can be more difficult to pick out subtle differences in road conditions, especially if roads were clear just minutes before.
These decisions are made even more difficult by the design of cars, Havas said, with their heated seats, quiet cabins, cup holders and surround sound.
"All these little luxuries make driving more comfortable and pleasant, but they may also be subtly preventing our brains from adapting to the new driving conditions outside of the car," Havas said.
Perception also plays a part in how seriously we take winter weather warnings issued by the National Weather Service. The NWS issues at least five types of alerts during incidents of winter weather, from the attention-getting blizzard and ice storm warnings to the less-noticed winter weather advisory.
"Frankly, I believe many interpret the word 'advisory', as 'no big deal', some perhaps even outright ignoring it," Erdman said. "However, a late-afternoon 1 to 3 inch snowfall, which may prompt an NWS winter weather advisory, can turn the afternoon rush hour into a mess."
On Jan. 4, 2016, the NWS in Taunton, Massachusetts, issued a winter weather advisory at 3:41 a.m., which advised that all untreated roadways would become slippery with only a trace of snow and visibility would be reduced at times.
Despite the fact that the advisory was repeated just before 11 a.m. and again just before 3:30 p.m., there were numerous wrecks in the area, including a multi-vehicle pileup near Duxbury. In nearby Marshfield, police reported 17 accidents involving 29 cars and a school bus in less than two hours.
"As a lifelong leadfoot driver, there's nothing scarier to me than that moment when the roads first become slippery, acquiring that light coating of snow or glaze of ice accumulation," Erdman said. "You're not only slowing down yourself and increasing following distance, but you're praying drivers around you are doing the same."
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