Why does 1.7 inches of snow cause over 200 traffic mishaps?
Light snow and wheel-track glazing the likely answers
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It’s a mystery of a Minnesota winter. How can a mere 1.7 inches of snow cause over 200 traffic mishaps?
The answer has much more to do with temperature than snowfall totals.
Couple inches
Snowfall totals were on the lighter side across the Twin Cities Thursday.
But what fell was more than enough to turn roads into crash test zones.
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The Minnesota State Patrol counted 252 accidents or spinouts with 18 injuries as of 11 a.m. Thursday.
All about temperature
It’s one of those ironies of a Minnesota winter. An inch of snow at 15 degrees can cause way more traffic problems that 6 inches at 30 degrees.
The reason is temperature.
Road chemicals just don’t work as well with pavement and air temperatures colder than 15 degrees. Take a look at temperatures in the Twin Cities this morning. Most of the snow fell with temperatures in the mid-teens.
Wheel-track glazing
The physics of snow, temperature, and driving make for some icy realities.
Wheel-track glazing occurs when ice crystals within the thin layer of snow are crushed beneath your warmer tires. The result can be rapid melting, then instant freezing.
Here’s more on wheel-track glazing from the Iowa Department of Transportation.
“Wheel-track glazing” is caused by warm tires trapping the ground level blowing snow. As more vehicles travel over the same wheel tracks a glaze of ice forms, which becomes very slippery.
The combination of light, blowing snow and cold surface temperatures could result in icy roadways due to a phenomenon called wheel-track glazing. “Wheel-track glazing” is caused by warm tires trapping the ground-level light, blowing snow. As more vehicles travel over the same wheel tracks, a glaze of ice forms that becomes very slippery. The condition is very difficult for Iowa Department of Transportation crews to treat because the ice is continuously forming on heavily traveled roadways.
It’s a reminder to pay as much attention to temperature forecasts during snowfall events. There is often better traction on roads with several inches of snow at 30 degrees, than with an inch at 10 or 15 degrees.
