Jeff Duntemann's Contrapositive Diary Rotating Header Image

February 14th, 2011:

Uphill Melts First

We’ve had a miserable cold winter here, and whereas we haven’t gotten any more snow than average, the snow that we’ve gotten has been a long time leaving. Over the past four or five days the temps have finally been trending up, and as the snow melted on our sidestreets I once again noticed something I’ve seen the last few winters: The uphill lane melts first.

It’s a fascinating business. It’s consistent, and there are a lot of stiff inclines here on the slopes of Cheyenne Mountain. No matter what street I drive on after a snowfall, it’s the uphill lane that melts first. So the citizen scientist in me started chewing on the question: Why?

My first hypothesis was that on the eastern slope of a mountain, roads running east and west have the uphill lane on the north side, meaning that the southerly winter Sun is more likely to fall unshadowed on the north-lying lane. This may be a factor on some streets, but I quickly found hilly streets running north and south and at odd angles. In all cases (I didn’t find even one exception!) the uphill lanes melted first. This was true even on the north sides of small hills where the road surface got little if any sunlight at all.

This left me only a single hypothesis: That car engines have to work harder to move a vehicle uphill, and therefore the undersurface of the car (engine and exhaust system) are hotter going uphill than downhill, when the engine is basically idling. Heat radiating from the undersides of uphill-traveling cars melts more snow than vehicles idling their way downhill. This is a suburban area rather than rural, and there are a lot of houses up here, all on smallish lots. So traffic is significant, especially at rush hours, when conga lines of minivans and four wheelers (necessary on winter roads with 12% grades) commute down and back to Colorado Springs.

I don’t know how true this is, nor how to test it in a controlled fashion. The snow is now gone, but come next week another experiment will be set up, and I’ll have a chance to look again. (I need to keep a camera in the car so I can snap a picture of the effect in action, something I haven’t done yet.)

If you’ve seen something like this happen in your area, let me know.