Extremely low air temperatures and windy conditions are causing black ice on area highways and on the interstate, the Minnesota Department of Transportation said in a Tuesday news release.  Black ice is a hard-to-see hazard that catches drivers off-guard, causing fishtailing, spinning and crashes.

Many crashes have occurred already on Interstate 35, MnDOT said.

“We have all of our changeable message signs lit warning motorists to slow down,” said Morrie Luke, MnDOT traffic engineer. “But some motorists are ignoring these messages and many have spun out.”

Black ice creates the appearance of a wet surface, but it is actually a thin, clear layer of ice on roads and bridges. Black ice forms when melting snow refreezes or when rain, drizzle, mist or fog freezes. It is most common at night and early morning when it is dark and temperatures are lowest.

Black ice often forms in tunnels and other shaded areas, on overpasses and bridges, and near lakes and rivers. The hazard can also form when snow temporarily melts from auto exhaust emissions or tire heat and from moisture vapor given off by industries located close to the highway.

Motorists should remember to:

  • Slow down on bridges, overpasses and tunnels and on all roads in the early morning when the air temperature rises faster than the pavement temperature.
  • Use a safe speed for winter driving conditions, regardless of the posted speed limit.
  • Keep a safe stopping distance from the vehicle in front of them.
  • Keep both hands on the steering wheel and eyes on the road, and stay alert.