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Illinois Department of Transportation

Winter Road Conditions

Winter road conditions can change quickly. Before you head out, take time to check road conditions on Getting Around Illinois. 

Covered

The road is completely covered and may have received some treatment. 

Mostly Covered 

The road is almost entirely covered and has received some treatments, but still has snow or ice on significant portions. 

Partly Covered

The road is partially covered. Traffic lanes are mostly clear. A small ribbon of snow on the road and shoulders may still be visible. 

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Fast Facts:

  • There are over 1,221 routes.
  • The average length of a route is 15-50 miles.
  • Routes run both day and night.
  • Multiple trucks are assigned to interstate and multilane roads.
  • IDOT maintains Interstates, U.S. Highways and State Highways.

Fast Facts:

  • Road salt lowers the freezing point of water, which can prevent snow from forming and melt existing snow/ice.
  • IDOT primarily uses rock salt along with liquid chemicals (salt brine or beet juice) to augment the rock salt. 
  • Liquid chemicals are used to prevent frost on bridges and prewet dry salt to help it stick to the road better.
  • IDOT treats bridges with salt brine 2-3 times per week to prevent frost accumulation.
  • Bridges are treated before a winter storm to ensure the first pass of a snow plow most effective. 
  • Salt loses effectiveness at lower temperatures:
    • Salt is spread when pavement temperatures are at or above 15°.
    • Additives are needed if below 15°.
    • No treatment is applied if snowfall is heavy or it's below 5°.
  • Salt isn't spread during heavy snowfall until most of the snow is plowed away. Sand may be spread for traction until the pavement warms.