Environment

Study suggests that stiffer roads would improve trucks' mileage

Study suggests that stiffer ro...
Traditional asphalt "sags" under the weight of transport trucks
Traditional asphalt "sags" under the weight of transport trucks
View 1 Image
Traditional asphalt "sags" under the weight of transport trucks
1/1
Traditional asphalt "sags" under the weight of transport trucks

Everyone knows that walking on soft sand is more difficult than walking on a hard sidewalk. By the same token, MIT scientists are now suggesting that if road surfaces were to be made stiffer, large trucks would use less fuel.

Asphalt may not seem particularly soft to us as we walk on it, but that's only because we don't weigh several thousand pounds. The heavy weight of a transport truck, on the other hand, causes the asphalt to deflect downwards slightly beneath each wheel.

As a result, the truck is perpetually in a state of trying to climb out of an ever-so-slight depression in the road. This means that it burns more fuel than it would otherwise, producing more carbon dioxide emissions in the process. According to MIT researchers Hessam Azarijafari, Jeremy Gregory and Randolph Kirchain, this problem could be alleviated if roads were made of stiffer materials.

These could include traditional asphalt, to which a small amount of relatively inexpensive synthetic fibers or carbon nanotubes were added – about 10 percent of the total mix would reportedly make a big difference. An alternative would be to use a larger grade of aggregate when mixing the asphalt, resulting in a finished product made up of more rock and less binder.

Yet another approach would involve simply making roads out of concrete instead of asphalt. Although this would initially be more expensive, the roads would last longer, meaning that costs would be reduced in the long run.

Based on the scientists' calculations, if 10 percent of US road surfaces were annually made stiffer over the next 50 years, a total of 440 megatons of carbon dioxide-equivalent emissions would be avoided. Although that represents just 0.5 percent of total transportation-related emissions for the period, it's still a significant figure.

That said, the researchers do admit that even though the stiffer roads would likely require fewer repairs than today's "soft" roads, the upfront changes in the construction process might initially make them more expensive.

A paper on the study was recently published in the journal Transportation Research Record.

Source: MIT

13 comments
paul314
What would that do to the suspensions of ordinary vehicles? Concrete has joints, and around here they tend to be unforgivingly bumpy.
Komakai.Okane
Isn't the resulting invention called a "train"?
Alistair Chapman
Did the study consider the tyres? Surely this would be a simpler way to reduce the rolling resistance?
WB
Ok a mile of road costs about 1-3 million dollars to build.
Adding 10% Carbon Nanotubes by weight - seriously? I love researchers who come up with practical and usable suggestions!
So let's see, a gram of carbon nanotubes costs USD 100. So their suggestion would change the cost of 1mile road to go from millions to billions!! Awesome let's do that so we can increase the fuel efficieny of a truck by 10%. Also the cost to fix harder roads are exponentially higher.
vince
Sure why don't we just also make it mandatory for the trucks to have steel wheels which being much harder than typical truck tires won't have all that nasty friction to deal with. Of course, slip n slide on water and ice might be a problems and the road damage per mile would be astounding. Nice try but not gonna happen in America it's too cheap. America won't build it's Interstates like Germany's Autobahns.
MQ
Is this not a reason why freeways are concrete ?- Much stiffer than an asphalt over compacted roadbase - as per regional roads.
Ralf Biernacki
"if 10 percent of US road surfaces were annually made stiffer over the next 50 years", the carbon footprint of the massive reconstruction work would far surpass any incremental savings, not to even mention the exorbitant financial outlay. Stiffening a road takes much more than just stripping the existing asphalt and repaving, and that's costly enough already. But to make a road stiffer, you need to replace the layers under the asphalt---practically rebuild the road. And BTW the math is wrong: 10 percent annually over 50 years is 500% altogether. I don't suppose the authors are proposing stripping and rebuilding all the roads in the US five times over, so I assumed the word "annually" is an error---the concept is preposterous enough even without it.
Charley Parker
What a great, futuristic idea. We could even make dedicated roads for freight out of steel, and the rolling efficiency would be so great that we could string multiple containers together in long chains, pulled by a single engine!
Saigvre
Hard truckin' truth, thanks. Forgot what it felt like to move a rig. Gonna be amazed if only 10% carbon fiber or graphene can stiffen up a road; concrete bases make a good start though. Good decarbonizing stuff and no lost rubber to the Miata or Aston Martin.
f8lee
I thought that as concrete cures it emits a large amount of CO2 - thus the reason construction is cited as major contributor to greenhouse gasses - from the WIkipedia entry called "Environment impact of concrete":
"The cement industry is one of the main producers of carbon dioxide"
Was this included in the calculus of saving emissions?