Which of the following is true about roadways on bridges and overpasses in cold, wet weather?
Answers
They tend to freeze before the rest of the road does.
They do not freeze because they are made of concrete.
They tend to freeze after the rest of the road does.
The Correct Answer and Explanation is :
The correct answer is: They tend to freeze before the rest of the road does.
Explanation:
In cold, wet weather, bridges and overpasses freeze before regular roadways for several reasons related to their structure and exposure.
- Exposure to Air: Bridges and overpasses are elevated structures with air circulating around them on both the top and bottom surfaces. This makes them more susceptible to temperature changes. When the temperature drops, the underside of the bridge cools down quickly because it is exposed to the cold air beneath it, while the ground underneath a regular road retains some warmth from the earth, providing insulation.
- Lack of Ground Insulation: Roads are typically built on top of the earth, which provides thermal mass that helps moderate temperature fluctuations. The ground underneath the road absorbs and stores heat, which can delay freezing. In contrast, bridges do not have this insulating layer and thus lose heat faster. As a result, the roadway surface on a bridge can become icy even if the surrounding ground is still above freezing.
- Faster Cooling: Since bridges are exposed to air from both sides, they lose heat more rapidly, meaning that when temperatures drop, the freezing point can be reached more quickly compared to roadways, which are insulated by the earth below.
This is why bridges and overpasses are often more hazardous in cold, wet weather, and drivers are advised to be cautious, even when the rest of the road seems clear. It’s a good practice to slow down and increase following distance, particularly when driving over these structures during freezing conditions.
Understanding this phenomenon helps drivers anticipate dangerous conditions and take necessary precautions to avoid accidents.