The Manitoba Driver, from Manitoba Public Insurance
November 2007

172 words
Bridges and overpasses hold hidden dangers

The onset of colder weather brings with it the seasonal hazard of icy bridges and overpasses.

“Motorists should pay attention to any signage that indicates an icy bridge ahead,” urges Clif Eden, manager of Road Safety for Manitoba Public Insurance. “You may not notice anything, but black ice blends perfectly with the asphalt and is often hidden beneath snow.”

There are a number of reasons that these structures develop black ice or surface frost more quickly than roads.

The first is that bridges are exposed to cold air from all sides. With roads, the ground acts as a protective insulator and prevents them from freezing over so quickly.

The location of bridges – over rivers that are frozen in winter or over other low-lying spots – also means they are often situated in colder-than-normal areas. And the materials used to construct bridges usually conduct heat efficiently, meaning they quickly assume the temperature of the surrounding air.

Exercise caution when traveling over these structures, and increase and decrease your speed gradually. Avoid changing lanes abruptly.

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© 2007 Manitoba Public Insurance

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