Ask a Trooper: Why do bridge decks freeze up faster than the rest of the roadway?

December 5, 2014 Updated Dec 5, 2014 at 7:49 PM CST

Question: Why do bridge decks freeze up faster than the rest of the roadway?

Answer by Sgt. Neil Dickenson of the Minnesota State Patrol: Bridges are made of steel and concrete which conduct heat well and the heat within the structure is released rapidly from all sides when temperatures drop.

When the bridge loses heat while being hit with freezing wind and air from all sides, it quickly responds matching the dropping temperatures; leaving icy bridge decks. I might add that bridges, by purpose, are often built above cold spots, like rivers, adding to this quick cool system.

A road doesnt have as many avenues for the heat to escape and thus doesnt cool as fast being insulated from the earth below. Additionally, asphalt roads do not conduct heat well and the response to frigid temperature is slower.

Do not use cruise control on snow/icy/wet roads and make sure to turns those headlights on when it is snowing/sleeting/raining/ or foggy.

If you have any questions concerning traffic related laws or issues in Minnesota send your questions to Sgt. Neil Dickenson Minnesota State Patrol at 1131 Mesaba Ave Duluth, MN 55811 (rr at, neil.dickenson@state.mn.us)."

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Ask a Trooper: Why do bridge decks freeze up faster than the rest of the roadway?