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I took a shortcut home on a gravel road last week and noticed that my FE was 5-10 mpg lower than I would get on the nearby concrete state highway at equivalent speeds. I have noticed that my FE also differs on other road surfaces (e.g. concrete vs. asphalt vs. chip and seal). What results have other people had?

i would imagine its the same as pedaling effort on a road bike: the smoother the better. there is a noticable difference between concrete, asphalt, and riding a paint line. of course there is a trade-off: less grip on a smoother surface.

The more I can hear road noise at a given speed, the more of 'my' fuel energy is being turned into sound. Entirely qualitative but it might be used to choose roads to travel if you have a choice.

However, if it is rainy and need to stop in a hurry, a noisy road could be a better choice :)

DAS

I have noticed that the newest highway surface in our county is noisy and fuel economy takes a big hit on it. The road appears flat and it doesn't matter going east or west, the fuel economy reeks. It is constructed of asphalt. The old concrete highway parallels it for about 8 miles. I can take it and even with 2 stop signs, end up with a 5 to 10 mpg increase for the 8 miles. I think the new asphalt road may contain recycled rubber from tires. I will try to find out this information from one of the state highway engineers. Does anyone know of a website that compares road friction in Illinois or any state?

Using the Prius MPG Simulator (http://privatenrg.com), FE drops by about 40% when going from smooth dry pavement to gravel at 35 MPH. Of course comparing specific performance of the Prius to that of your car is not apples-to-apples. But the point is valid: Rolling resistance is substantially higher on gravel than on the road.

I have noticed that the newest highway surface in our county is noisy and fuel economy takes a big hit on it. The road appears flat and it doesn't matter going east or west, the fuel economy reeks. It is constructed of asphalt. The old concrete highway parallels it for about 8 miles. I can take it and even with 2 stop signs, end up with a 5 to 10 mpg increase for the 8 miles. I think the new asphalt road may contain recycled rubber from tires. I will try to find out this information from one of the state highway engineers. Does anyone know of a website that compares road friction in Illinois or any state?


Road noise is probably a reasonably good indicator of efficiency, but I'm thinking that asphalt is probably flexible in a way that quietly consumes energy too. Asphalt usually is reasonably quiet if it has been rolled properly. If a paved road is really loud I would guess that it has another kind of seal coat or didn't get rolled well enough (I can just hear the engineer saying "don't worry, the traffic will take care of that after a little while.")

They have started putting little grooves in the concrete roads here. They rob me of mpg.

Then they redid large sections of hwy 75. The north bound work is good. The south bound work sucks. They used asphalt. Going north they laid down a course layer then top coated it. Really pretty smooth. Then on the south bound they did two course layers. One of the areas going south use to be a good fas. If done right a 1.5 mile fas. Or at worse a 2 .5 mile P&G. Either way it was a real good mpg booster. Now you cant even bleed throttle off on it. The college boys in OKC saw to it that part of the road was ruined.

When questioning the hwy dept. Or any of Oklahoma's idiots of power concerning stuff like this all you get is canned spam for answers.

As for the gravel roads. Just yesterday the wife and I had to move our oldist daughter and two grandkids back in with us. ( GGGGRRRRRRRR ) We ended up having to drive the Rangealturd and Accord on 7 miles of very hilly gravel road. I didnt put the SG in either of the rides for the trip. But,,, I know it sucked the life right out of the tanks. I had to stop and tell the wife to back off. Not that she was real close to the Rangealturd. But I could see in the reveiw how the truck was throwing rocks at the Accord. I couldnt believe she was going to follow me down the gravel road that close to me. It just amazes me how stupid she can get at times. I honestly have no idea how she made it thru college. Hills were so steep I had to pull then in 2nd gear in the truck. Guess where to loose gravel was going? Right on the Accord. DUH!!!!!

psy

I'd bet if was painted with fingernail polish ,she'd have been a mile back ;) ...sorry had to say it .

Noise isn't a totally reliable indicator of rolling efficiency. Smooth concrete roads are noisier than asphalt, but have better FE.

Hi basjoos, ya made me google it :Banane37:

Starting on about p 16 of this report:

http://www.eapa.org/START/positionprs_publications/papers/Fuel%20Efficiency%20Report.pdf

There is info on both the surface roughness and bed flexibility aspects of the question. I have not the skills to provide a decent summary.

I do like the peace and quiet of new asphalt, but I now agree that it may not be the 'cheapest ride'.

So good hypermiling routes must be chosen with consideration of 'topography' down to the 0.5 mm scale. What a bother.

DAS

Hi basjoos, ya made me google it :Banane37:

Starting on about p 16 of this report:

http://www.eapa.org/START/positionprs_publications/papers/Fuel%20Efficiency%20Report.pdf

There is info on both the surface roughness and bed flexibility aspects of the question. I have not the skills to provide a decent summary.

I do like the peace and quiet of new asphalt, but I now agree that it may not be the 'cheapest ride'.

So good hypermiling routes must be chosen with consideration of 'topography' down to the 0.5 mm scale. What a bother.

DAS

Thanks for the citation DAS

I wasn't familiar with some of the terminology though, for example I think Europe may use a different nomenclature for aggregate size. To the extent that the author drew conclusions that I could understand they seemed to be that smooth asphalt and smooth concrete were probably about the same for light vehicle FE, but that heavy trucks suffered FE losses on asphalt due to flexing of the asphalt particularly in the summer. Unfortunately concrete and asphalt "about the same" was up to a 3-4 % difference.

When I visited Europe years ago I remember thinking that their asphalt was a little smoother than in the US, so I'm not sure if we have much of "dense asphalt concrete" that they tested as appearing to be the best. I think much of our asphalt is "stone-mastic" (at least that's what they sell at the DIY stores) which one sudy estimated as costing about 3% FE, which appeared to be inside the study's margin of error.

I'm hoping there is better data (tighter margins of error?) out there that references the pavement terminology I am familiar with.

For now I think would go with Basjoos' analysis that asphalt is worse if I had to choose between asphalt and concrete.

The key for maximum FE is HARDNESS. Concrete roads are much harder than asphalt roads. Especially in sunny hot weather, asphalt can get very soft. As a kid, my bicycle kick-stand would sink into asphalt on very hot days.

Hardness is even more important than smoothness or quietness. The harder the surface, the better the tires roll along. A good parallel is, have you ever roller-bladed or roller skated? Do you know how difficult it is to skate and roll on softer surfaces like asphalt, artificial tennis courts, wood floors, rubber school tracks etc? But on a smooth hard cement surface, those skates will really roll!

Another problem with black asphalt (mostly summertime) is tire wear. Being black, the asphalt absorbs so much heat on sunny days. HEAT is what wears out the tires. Studies show that tire wear is extrememly small during the rain or cold or snow, or at slow speeds. But long, high speed freeway trips on asphalt on hot sunny days, really wears the rubber quickly.

Please, give me white, hard concrete any day!!