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How much warming occurs on a road surface due to traffic?

It’s got to be a somewhat measurable amount. During light snowfall, there is always snow accumulation on the shoulder before the plow comes through, but the snow landing in the lanes melts instantly. I don’t think it is solely because of the salt use but maybe I’m wrong about that.

There has probably been research on this. State highway or transportation departments, or the US DOT may have employees who could direct you. Maybe the IIHS - Insurance Institute for Highway Safety, too. Someone somewhere has taken this question beyond the barstool.

I already posted several references to technical discussions on it. It’s always amusing to see speculative, qualitative assessments based on preconceived notions. We all do it. Even professional engineers tend to make conclusions based on what they think may be happening. It’s always fun to see those notions proven wrong…

Tracks on the road way are probably a result of the sum total combinations of all the things mentioned. There is heat from tires (it’s not a single car going by), pressure displacement (the surface is permeable as well), pickup and flinging of the water, convective effects of the vehicle motion moving the surrounding air etc etc etc. To say, without any data to back it up, that heat from tires is inconsequential is funny especially given some of the scientific study put into that topic stating it is significant. The tire gets heated by flexing and so does the tire to road interface due to squirming. Our tires wouldn’t wear away so fast if they weren’t constantly being scrubbed even when traveling mostly straight. Heat is heat, it doesn’t magically disappear…


I didn’t say it was inconsequential, I said it wasn’t all that significant, and I stand by that statement.

The tire wearing from its own heating was not the subject of discussion and is irrelevant to the question asked. The tire is in constant contact with itself and therefore the heat generated by the tire is significant to the tire. Not so much the things the tire very briefly rolls over.

Even if the tire heats up to 120 degrees, which would be a pretty good trick for a normal street car in the winter on ice, you generally have less than 40 square inches worth of contact patch, which means, especially at the kinds of speeds required to heat the tire that much even in the summer, the heated tire is in contact with any given section of road for a small fraction of a second before it’s gone.

In the same vein as the fact that you can wave your fingers through a flame without setting yourself on fire, the heat transfer just isn’t going to be very high because of the very brief time span of contact between the “hot” tire and the road. It will still be there, but other factors will be far more significant.

I do realize that a a 3.2 degree increase in temperature is statistically significant, but I also realize that 3 of those 3.2 degrees are heating the tire track up to the temperature of the rest of the road because the tire tracks, according to your linked study, are colder than the surrounding road when cars aren’t passing over them. This means the tire tracks during times of heavy vehicle passage, are all of 0.2 degrees hotter than the surrounding pavement. While that is definitely non-zero and may even be considered significant for the purposes of the study, as far as it being enough to melt snow? Only if the rest of the road is already within less than 1 degree of being able to melt the snow un-aided by tires.

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I bet (especially in places like Texas) it’s the road that heats the tire, rather than the reverse.


Off topic again. When I was a kid I spent 25 cents or so on a mail order book “Feats of Strength”. Kinda fun. How to impress your friends. Talked about how to pull a railroad car, bending a bar etc. However I did have a guy that worked for me that could rip a Minneapolis phone book in half (about 4"). It was no trick like in the pamphlet. I didn’t believe him and he did about three in a row. Don’t make him mad.

I’ll weigh in a little here just based off of my best educated guess.

the tracks from rain or snow are more likely due to excess moisture not being allowed to sit on the road surface. each time a tire rolls over it again, it will pick up some moisture and dissipate it in the form of mist or evaporation etc.

thinner layer of moisture + minimal surface heat from tires/friction + larger internal heat from absorbing the sun/atmospheric temps = clears quicker than standing moisture next to it.

a little side reading for you: An interesting report of this was done by NASA for landing performance on a runway

page 13 or so goes into the dissipation. which seems pretty fast especially considering the much larger friction forces/heat from airplane impact vs automobiles.

In addition to what the tires do, there is also the effect of radiant heat from the exhaust system. And all the while, moisture in exhaust gasses goes somewhere: downward to the pavement fairly quickly in very cold conditions, dissipated to some extent by air movement.

Tomato, tomahtoe…

Think what you will, the linked analysis pretty much defines how much heat is transferred using fairly sophisticated analysis tools. The other links I supplied back it up, one being from NASA. I guess I place more trust in those articles than what you surmise to be true.

Not sure if this relates to what you’re asking, but last year I saw an article out of Australia wherein they did a test. They painted one lane of a highway white and found out under the summer sun that surface was 7 degrees Celsius cooler than the side that remained unpainted asphalt. It seems to me that while this might have a negligible effect on tire performance (life, traction) it could have a major effect on local climate if done universally.