Hey Ray! The Science Behind What Causes Bridges To Freeze First

PITTSBURGH (KDKA) -- Bridges are great. They make getting from place to place easier, even with obstacles in the way.  Pittsburgh has many obstacles like river valleys and rivers, thus Pittsburgh has a lot of bridges.  446 of them!

With bridges, there are additional things to be alert for in colder weather, such as ice.

Bridges are made of steel and concrete. Roadways, on their own, would heat up and cool down quickly, too, because those materials are what we call conductors.

They transfer heat from one place to another quickly.

In the world of thermodynamics, heat is transferred from warmer things to colder things.

This means that these materials pass their heat to the colder air above them.

When just looking at their materials, roads and bridges lose heat evenly.

Standard roads, or roads on the ground have a little help staying warm, though.

The roadways on the ground will lose heat much more slowly because they have the ground to insulate them or help them hold heat longer.

Sort of like an unzipped coat. You are still losing heat, but not as quickly as no coat at all.

Bridges, on the other hand, don't have the ground to help keep them warm, or at least to help slow the cooling process.

Since roadways on the ground are like wearing an unzipped coat, elevated roadways, or bridges, are like not wearing a coat at all.

They lose heat on all sides simultaneously, meaning they can reach freezing temperatures much faster, allowing ice to form faster.

These same principles go for elevated porches and the stairs that lead to them, too.

I am guessing there are more than 446 porches in Pittsburgh, though, so make sure you pay close attention to these, too.

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