How not to drive into a pond

When a driver's window fogged up, she tried to pull over. Instead, she ended up in a highway holding pond in Bloomington. Minnesota State Patrol via Twitter

It was a heartwarming, and potentially tragic, moment yesterday when a woman drove into a retention pond on a ramp at the intersection of U.S. Highway 169 and Interstate 494 in Bloomington.

People passing by stopped and were pretty smart about how to get the woman out of her truck, which was nearly submerged. They pulled a pallet off a truck to distribute their weight on the thin ice, and the woman used a fire extinguisher to break the window.

All good ideas. And there are more if it happens to you.

“You can pull your headrest out and use the prongs from that to break through the vehicle,” State Patrol Lt. Tiffani Nielson said. “If you ever feel your vehicle is going into a body of water you should try to roll the windows down right away.”

There’s a lesson in how the accident happened, too.

The State Patrol said the truck’s windows had fogged up and frozen with yesterday’s cold temperatures so she couldn’t see where she was going, and was going to pull over to clear things up.

Why does this happen?

Here’s some science from Indiana Public Media.

This is why windows fog up in a car full of people on a cold day. Water vapor is first exhaled into the air by passengers in the car. Then because the car windows are colder than the dew point air close to the glass cools to below the dew point as well, causing water vapor in this air to condense and stick to the windows.

Turning up the defroster will help, if it’s working and you’ve got the time, and if you don’t normally have your heater set to “recirculate,” which will only make things worse (More tips from the the Department of Physics at the University of Illinois)

There’s an easier and quicker way. Open your window.

Opening the window cures the problem by reducing the temperature of the air against the inside of the window, and the drier air will clear the humidity created by your breathing, and quickly evaporate the frost on the window.

It’ll be chilly, Allstate notes, but it beats driving into a pond.