A Discussion of Ice and Roads

Overheard at the grocery store: "It's 35 degrees and I didn't know when the bridges would freeze." Well, I don't know exactly either, but I can tell you they won't freeze until the air temperature gets to 32 degrees. Bridges do freeze before roads, but for any ice formation the temperature still has to drop to 32 degrees. Roads may not ice over until a lower temperature because the ground underneath the road helps keeps the road surface warmer. It takes longer for the ground temperature effect to be overcome by the cold air temp. Bridges freeze earlier because they have only air underneath them and are able to cool faster than the roads.

So, how do you drive safely on a potentially icy or snowy road? Contrary to local opinion, it's not impossible or else NYC, Chicago, Boston, Minneapolis-St. Paul, Cleveland, Buffalo, Denver, Montana and other places north would be completely paralyzed most of each winter. My advice: slow down and increase your following distance. The purpose of a decent following distance with bad road conditions is the same as with good road conditions: to provide you with enough time and distance to avoid hitting the vehicle in front of you. I realize that you are an excellent driver, have the reflexes of a superhero and can move your foot from the gas pedal to the brake at the speed of light, but I'm willing to bet your car won't go from 70 mph to zero in less than 20 feet. My *motorcycle* won't do that and it only weighs a couple hundred pounds. If you have a following distance that is shorter than your stopping distance, you're going to hit the vehicle in front of you if it happens to stop or even slow down suddenly for any reason.

What is a good following distance? For dry, clear road conditions, at least two seconds between cars and maybe three when following a motorcycle or truck. For wet or slick road conditions, I usually double that. When you're following a truck, you should at least be able to see the driver's side mirror and not just when you pull to the left side of the lane. While you're at it, refrain from passing trucks on the right and from hanging out in their blind spots. If you cannot see the driver in the mirror, figure they cannot see you. Despite popular rumor, you can indeed maintain decent following distance even in busy traffic situations. I've managed to do it in downtown Chicago during peak summer traffic, you can manage it in a city of 60,000 during the "rush hour". It's not a race. It's ok if other cars are in front of you.

End the lecture/rant/public service announcement for the day.


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