# How much warming occurs on a road surface due to traffic? **URL:** \ **Category:** General Discussion\ **Created:** [January 14, 2020, 8:25pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525 "2020-01-14T20:25:22Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Waterbuff](https://avatars.discourse-cdn.com/v4/letter/w/f07891/32.png) [@Waterbuff](https://community.cartalk.com/u/Waterbuff)\ **Post date:** [January 14, 2020, 8:25pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/1 "2020-01-14T20:25:22Z")
Another topic asking for thoughts – road surfaces are likely to be warmed up by the friction of tires traveling on them. But how much warming happens? I seem to recall that after some rain, the “tracks” where tires travel seem to dry faster than the rest of the road surface. So that’s one possible data point. Another data point might be the similar effect that seems to occur with (light) snow, which seems separate from just physical removal of the snow. A third data point is that tires warm by about 50 degrees F at highway speeds, which suggests some warming of the road surface where there’s continuous ample traffic (like stretches of some interstates). ---
**Author:** ![VOLVO-V70](https://avatars.discourse-cdn.com/v4/letter/v/8e8cbc/32.png) [@VOLVO-V70](https://community.cartalk.com/u/VOLVO-V70)\ **Post date:** [January 14, 2020, 8:31pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/2 "2020-01-14T20:31:30Z")
Is this another Bar Room discussion like your turning tires while stationary ? ---
**Author:** ![Waterbuff](https://avatars.discourse-cdn.com/v4/letter/w/f07891/32.png) [@Waterbuff](https://community.cartalk.com/u/Waterbuff)\ **Post date:** [January 14, 2020, 9:47pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/3 "2020-01-14T21:47:30Z")
> [@VOLVO\_V70](#): > > Is this another Bar Room discussion like your turning tires while stationary ? only if you want to drink while joining in or reading… NO bar fight(s) intended 😉 yet I am seriously interested in input / thoughts / leads – kind of like in the spirit of the two brothers bouncing an idea around (and like the turning tires while stationary, this is about a real world thing that happens every day AND does not have much (if any) info on CarTalk when I searched for it btw, I did learn some relevant things from the turning tires thread) ---
**Author:** ![VOLVO-V70](https://avatars.discourse-cdn.com/v4/letter/v/8e8cbc/32.png) [@VOLVO-V70](https://community.cartalk.com/u/VOLVO-V70)\ **Post date:** [January 14, 2020, 9:53pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/4 "2020-01-14T21:53:12Z")
You really think anyone is going to spend time and money on a survey like this ? Too many factors to even reach a marginal figure 🤔 Road construction ( asphalt or concrete ) - ambient temperature - tire thread of the majority of vehicles - average vehicle weight - vehicle speed - even the ground temperature . ---
**Author:** ![Waterbuff](https://avatars.discourse-cdn.com/v4/letter/w/f07891/32.png) [@Waterbuff](https://community.cartalk.com/u/Waterbuff)\ **Post date:** [January 14, 2020, 10:14pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/5 "2020-01-14T22:14:57Z")
As I said, NO bar room fights intended – I hope you can share that sentiment. And you should NOT think I’m expecting someone “to spend time and money on a survey like this” “Too many factors to even reach a marginal figure” Thanks for your personal view – although I don’t know what “figure” you have in mind. OTOH, any information is better than no information, and this forum makes possible the benefit of additional observations and experiences by others – I hope you aren’t trying to discourage others from participating (or even starting threads) “Road construction ( asphalt or concrete )” yes, observations and experiences welcome “ambient temperature” yes, observations and experiences welcome “tire thread of the majority of vehicles” yes, observations and experiences welcome – although that probably averages out to be about the same on busy, continuous ample traffic stretches of road “average vehicle weight” yes, observations and experiences welcome – although that probably averages out to be about the same on busy, continuous ample traffic stretches of road “vehicle speed” yes, observations and experiences welcome – although that’s a relatively narrow range on busy, continuous ample traffic stretches of road “the ground temperature” yes, observations and experiences welcome – in fact, I left out the observation that in summer months in some places, road surfaces will remain warmer than air temp for some time after dark, while in winter months in some places, road surfaces will remain cooler than air temp for some time after daybreak ---
**Author:** ![MikeInNH](https://avatars.discourse-cdn.com/v4/letter/m/a587f6/32.png) [@MikeInNH](https://community.cartalk.com/u/MikeInNH)\ **Post date:** [January 14, 2020, 10:15pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/6 "2020-01-14T22:15:58Z")
There definitely is heat being generated, but not sure exactly how much. ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [January 14, 2020, 10:21pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/7 "2020-01-14T22:21:57Z")
> [@Waterbuff](#): > > I seem to recall that after some rain, the “tracks” where tires travel seem to dry faster than the rest of the road surface. My thought is the tracks are due to the displacement of water from tires rather than heat ---
**Author:** ![Rod-Knox](https://avatars.discourse-cdn.com/v4/letter/r/a183cd/32.png) [@Rod-Knox](https://community.cartalk.com/u/Rod-Knox)\ **Post date:** [January 14, 2020, 11:38pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/8 "2020-01-14T23:38:39Z")
I have run tests on tires operating on an 8’ diameter test wheel and the tires did get noticeably hot as speed increases and inflation pressure decreases as did the test wheel. All tires were run until they failed with the pressure being lowered and the speed increased until the tire separated and at that time tread rubber would be gumming up and smoking on the test wheel. ---
**Author:** ![bing](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bing/32/4619_2.png) [@bing](https://community.cartalk.com/u/bing)\ **Post date:** [January 15, 2020, 12:37am UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/9 "2020-01-15T00:37:45Z")
I gotta believe it is negligible. Just got back off the road from wet from snow and as soon as it cools down a little that wet will be ice, regardless of traffic volumes. In traffic, the tracks on a wet road will dry faster the same as if you dry your hands on a towel. The tires are picking up the water and spraying it away. Not much to do with heat in my view. ---
**Author:** ![Waterbuff](https://avatars.discourse-cdn.com/v4/letter/w/f07891/32.png) [@Waterbuff](https://community.cartalk.com/u/Waterbuff)\ **Post date:** [January 15, 2020, 7:32pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/10 "2020-01-15T19:32:06Z")
> [@MikeInNH](#): > > There definitely is heat being generated, but not sure exactly how much. Thanks > [@Barkydog](#): > > My thought is the tracks are due to the displacement of water from tires rather than heat Good point, although I wonder if there are examples of light snow conditions where other effects are seen – like where a dusting of snow is displaced (or pressure melted) by tire traffic and then the small amount of liquid is heat evaporated rather than displaced. ---
**Author:** ![Waterbuff](https://avatars.discourse-cdn.com/v4/letter/w/f07891/32.png) [@Waterbuff](https://community.cartalk.com/u/Waterbuff)\ **Post date:** [January 15, 2020, 7:37pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/11 "2020-01-15T19:37:14Z")
> [@Rod\_Knox](#): > > I have run tests on tires operating on an 8’ diameter test wheel and the tires did get noticeably hot as speed increases and inflation pressure decreases as did the test wheel. If I may ask, what surface were in contact with the test tires and did that surface get hot? > [@bing](#): > > Just got back off the road from wet from snow and as soon as it cools down a little that wet will be ice, regardless of traffic volumes. Thanks – and it makes me think of the reverse condition: as conditions warm up, do the tire traffic tracks in light snow or a little ice melt faster than the adjacent areas not in the tracks? Your condition probably happens a lot in some places as the sun sets and temperatures cool while the reverse happens after sun rise and as temperatures increase. ---
**Author:** ![bing](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bing/32/4619_2.png) [@bing](https://community.cartalk.com/u/bing)\ **Post date:** [January 15, 2020, 7:43pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/12 "2020-01-15T19:43:58Z")
Yes of course, where salt has been applied, the tracks are usually the first to melt leaving snow or ice in the center and sides for a while. I don’t think it’s got much to do with tire heat though. ---
**Author:** ![Rod-Knox](https://avatars.discourse-cdn.com/v4/letter/r/a183cd/32.png) [@Rod-Knox](https://community.cartalk.com/u/Rod-Knox)\ **Post date:** [January 15, 2020, 7:58pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/13 "2020-01-15T19:58:51Z")
The test station looked similar to this [https://chantengineering.com/products/testing-machinery/tire-testing/](https://chantengineering.com/products/testing-machinery/tire-testing/) and the contact surface was similar in texture to crocus cloth but with years of use there was a heavy coat of rubber at the center. ---
**Author:** ![TwinTurbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@TwinTurbo](https://community.cartalk.com/u/TwinTurbo)\ **Post date:** [January 15, 2020, 8:08pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/14 "2020-01-15T20:08:44Z")
So here’s a whitepaper I found that contains information related to heat conduction to the road surface. Granted it is related to race tires but it outlines the major paths and their relative contribution: > **[Izze\_Racing\_White\_Paper\_Tire\_Temperature.pdf](https://www.izzeracing.com/products/ewExternalFiles/Izze_Racing_White_Paper_Tire_Temperature.pdf)** > > 4.26 MB > The majority of a race tire’s heat is lost at the tire-road and tire-air (external) > interfaces. Assuming the tire is hotter than the ambient, heat is lost at the > tire-road interface from conduction into the ground, and at the tire-air > interface from forced convection with the ambient air. Heat losses from > radiation are only significant for temperatures \> 100˚C and are often ignored. > However, heat to and from the tire can also be managed at the wheel-tire > interface; brakes feed temperature into the wheels & tires but wheels can > also be used to cool & thermally manage the tire. > Given the significant heat losses at the tire-road interface and transient heat > generation at the surface (surface heat generation is highly dependent on slip > ratio, slip angle, and load), a race tire’s surface temperature fluctuates rapidly > with dynamic loading. EDIT: Here’s another source of info: [https://www.researchgate.net/publication/266341564\_Effects\_of\_Vehicle\_Heat\_on\_Road\_Surface\_Temperature\_of\_Dry\_Condition](https://www.researchgate.net/publication/266341564_Effects_of_Vehicle_Heat_on_Road_Surface_Temperature_of_Dry_Condition) > **[19760007024.pdf](https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19760007024.pdf)** > > 69.44 KB ---
**Author:** ![Waterbuff](https://avatars.discourse-cdn.com/v4/letter/w/f07891/32.png) [@Waterbuff](https://community.cartalk.com/u/Waterbuff)\ **Post date:** [January 15, 2020, 8:18pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/15 "2020-01-15T20:18:48Z")
> [@TwinTurbo](#): > > So here’s a whitepaper I found that contains information… Wow! Thanks very much! [edit: interesting that tires with less tread (and/or less load) apparently generate less heat, and so would have less heat to transfer to the road surface or to the air] ---
**Author:** ![Waterbuff](https://avatars.discourse-cdn.com/v4/letter/w/f07891/32.png) [@Waterbuff](https://community.cartalk.com/u/Waterbuff)\ **Post date:** [January 15, 2020, 8:20pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/16 "2020-01-15T20:20:27Z")
> [@Rod\_Knox](#): > > The test station looked similar to this… Thanks for that! ---
**Author:** ![common-sense-answer](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/common-sense-answer/32/716_2.png) [@common-sense-answer](https://community.cartalk.com/u/common-sense-answer)\ **Post date:** [January 15, 2020, 11:53pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/17 "2020-01-15T23:53:42Z")
> [@Waterbuff](#): > > Another topic asking for thoughts – road surfaces are likely to be warmed up by the friction of tires traveling on them. > > But how much warming happens? I always hate saying, _"don’t know, don’t care, but…_" Running through the changes going through the stages Coming round the corners in my life Leaving doubt to fate staying out too late Waiting for the moon to say goodniiiigh-hi-hi-hite And I could cry for the time I’ve wasted But that’s a waste of time and tears And I know just what I’d change If I went back in time somehow But there’s nothing I can do about it now _Lyrics by Beth Nielsen Chapman, performed………… by Willie Nelson_ _ **CSA** _ 🌴 🕶 🌴 ---
**Author:** ![bing](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bing/32/4619_2.png) [@bing](https://community.cartalk.com/u/bing)\ **Post date:** [January 16, 2020, 3:35am UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/18 "2020-01-16T03:35:51Z")
> [@Waterbuff](#): > > I wonder if there are examples of light snow conditions My experience with light snow is the tires compact the snow into ice. Light snow is sometimes worse than a heavier snow. ---
**Author:** ![MikeInNH](https://avatars.discourse-cdn.com/v4/letter/m/a587f6/32.png) [@MikeInNH](https://community.cartalk.com/u/MikeInNH)\ **Post date:** [January 16, 2020, 3:29pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/19 "2020-01-16T15:29:19Z")
> [@bing](#): > > My experience with light snow is the tires compact the snow into ice. Light snow is sometimes worse than a heavier snow. Light snow means colder temps…so it can quickly turn to ice and make for slick driving conditions. When my middle child was new to driving…one morning it snowed about 1/2" and the temps were below 20. I told my son as he drove off to school to be careful because the roads were going to be slick. Luckily he heeded my warning. Said he saw many cars off the road and a 5 car crash on the way to school. ---
**Author:** ![shadowfax](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/shadowfax/32/13026_2.png) [@shadowfax](https://community.cartalk.com/u/shadowfax)\ **Post date:** [January 16, 2020, 4:03pm UTC](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525/20 "2020-01-16T16:03:35Z")
> [@Waterbuff](#): > > I seem to recall that after some rain, the “tracks” where tires travel seem to dry faster than the rest of the road surface. Better explained by the fact that tires are designed to fling the water out to the sides and therefore out of the “tracks.” The tire does briefly heat the road under it, which is why you slide on ice. The tire melts the top layer of ice, and that water makes it easy to slide around on ice. The same mechanism is what causes you to slip while walking on ice. When it’s extremely cold, ice actually isn’t very slippery when you walk on it because the pressure of your weight can’t melt it before you’ve taken your next step. The heating is more from compression due to the weight than from the tire being warm. Any time you change something’s shape, you end up with heat as a byproduct (which is why it’s always so funny in movies when they want to show someone is strong, so they have him bend a steel bar. Thing would be red hot if you bent it that fast). You’re pressing down on the road with a 3,000 pound plus vehicle - that’s gonna heat it up too. But unless you’re driving something like NASA’s crawler transporter, the heating isn’t going to be all that significant, especially since you’re probably moving over any given section of road at a pretty good clip. [Next page](https://community.cartalk.com/t/how-much-warming-occurs-on-a-road-surface-due-to-traffic/156525.md?page=2)