In road-building circles, the “concrete vs. asphalt” debate is every bit as intense as that drunken discussion (eventually devolving into a weepy shouting match) every year at Thanksgiving dinner between your right-wing uncle and your pinko vegan cousin.
On the rhetorical battleground, one of the strongest anti-concrete arguments has always been: “So pricey!” But perhaps that is changing. In Minneapolis, when bids came in on a project that includes new bus lanes and wider sidewalks (on Marquette and Second Aves near the convention center, for those familiar with the local terrain) the concrete and asphalt options cost more or less the same, according to a local business paper.
The underlying trend here is that asphalt’s price is closely tied to the price of oil. And when a barrel of crude when into three-digit land last year, asphalt was suddenly as expensive as concrete.
Even though the price of asphalt has come down a bit recently (according to many reports), this could still be a key moment in the debate.
We’ll take the opportunity to pick sides a bit and say we prefer using concrete whenever possible. Yes, it’s bumpy and loud to drive on and the initial construction costs have historically been a lot higher. But it’s also light of shade — that is, it absorbs a lot less heat. New concrete has an albedo as high as 0.80 (meaning it reflects about 80 percent of the sun’s heat). New asphalt has an albedo as low as 0.05 (it absorbs 95 percent). That’s a *huge* difference — greater, in fact, than the difference between snow and seawater.
As we wrote about here and here, a trio of well-regarded scientists have argued very persuasively that all the dark rooftops and roadways in our cities are heating up the planet, and we could buy a lot of time–think 20 years–in dealing with climate change if we lightened up on the double. Steven Chu, our Nobel laureate Secretary of Energy, has even weighed in in support of the idea. (We think he should put some stimulus money where his mouth is.)
We have a hunch that oil prices might headed back over $100/barrel in the next year or two. If that scenario plays out, it might offer a perfect opportunity to start migrating over to lighter pavements as a matter of national (and international) policy. Let the Great Whitening begin.
July 7th, 2009 at 4:33 pm
You’re absolutely correct that new asphalt is incredibly dark and heat-absorptive. However, have you ever noticed an asphalt pavement that’s only a year old? And have you ever performed a LCCA for a pavement? That one year savings doesn’t add up to much over a 20-30 year analysis period. Besides, I’d like to see a piece on the research currently being done in the field of asphalt pavements. You might be shocked to learn how much effort and how quickly the knowledge is advancing.
July 7th, 2009 at 4:45 pm
Very interesting stuff and here’s a bit of a curveball to mix it up a bit: What about cycling? It’s subtle but to the tuned rider asphalt is much more pleasant to ride on. I’d be curious to know just what sort of effect an all concrete infrastructure would have on ridership. Doubt many would complain outright but would it subtilely wind up discouraging cyclists? Or does it have the same effect of drivers too, amounting in a wash?
July 7th, 2009 at 5:39 pm
Is this a veiled admission that CO2 has not been the main driver of climate change?
July 7th, 2009 at 6:00 pm
Whoa,
Asphalt albedo tends to remain very low, even with aging. It would be interesting to hear more about research being done to raise the albedo of asphalt though. Please drop me a note if you think there’s any particularly promising work going on in that field (jr -at- infrastructurist).
Concrete, just by tweaking the blend a bit, can be made to be relatively high albedo, even with age.
Danny,
This.
JR
July 7th, 2009 at 9:57 pm
Dumb question, perhaps. Is there something with which we could paint our dark roofing shingles?
July 8th, 2009 at 12:17 am
Let’s not forget that the primary purpose of a road is to carry traffic and not fall to pieces. In my experience, concrete seems more prone to creation of large potholes that kill tires, wheels, and suspension pieces. Once a bit of concrete is nicked off at an expansion joint, the damage seems to spread quickly, whereas asphalt seems more durable over a longer time.
July 8th, 2009 at 8:11 am
Wouldn’t the roughness of concrete lead to lower fuel efficiencies?
What lifespans are we looking at here?
I was hoping, based on the picture, to see an article on porous concrete and asphalt. Huge, water-shedding parking lots are a problem here around Pittsburgh where we have numerous small and narrow, but heavily populated valleys that tend to have miserable floods at least once a year.
July 8th, 2009 at 9:17 am
[...] those white roads… [...]
July 8th, 2009 at 10:19 am
[...] bright ideas from around the network: The Infrastructurist calls for climate-friendlier concrete roads; Philadelphia Bicycle News compares the $22 million [...]
July 8th, 2009 at 10:23 am
[...] bright ideas from around the network: The Infrastructurist calls for climate-friendlier concrete roads; Philadelphia Bicycle News compares the $22 million [...]
July 8th, 2009 at 10:57 am
[...] yield a greener and leaner transportation system. More bright ideas from around the network: The Infrastructurist calls for climate-friendlier concrete roads; Philadelphia Bicycle News compares the $22 million [...]
July 8th, 2009 at 12:22 pm
[...] bright ideas from around the network: The Infrastructurist calls for climate-friendlier concrete roads; Philadelphia Bicycle News compares the $22 million [...]
July 8th, 2009 at 1:32 pm
Perhaps this is a dumb question… but does the albedo of roads really matter at all? If the sun’s rays are already in our atmosphere, will the light (and heat) reflected from a concrete street remove itself from the atmosphere or just reflect it only other lower albedo structures and “things” around and not really have any impact? We’re not talking about a closed system here…
And what is the difference in climes that are drastically different in different parts of the year, like Chicago and Minneapolis. I can see where the pavement would heat up in the summer… but might darker pavement absorb what heat and light is available in the winter and decrease the amount of salt etc needed to deice the roads?
I think an initiative to study the roofs of buildings and other “things” between roads would prove much more fruitful. A rooftop with a garden as opposed to a blacktop (or even one painted white) is going to use the sunlight instead of just reflecting it.
Addressing a question above in regards to porous roads…
I think, in general, though roads do certainly have runoff, it is controlled decently. Again, the runoff that should be focused on is that of parking lots and buildings. A gutter system is a perfect example of a collection of rainwater with a distribution in several specific locations around a building or a house. This will increase runoff and erosion in those places and likewise increase runoff near streams and rivers as the water, with no place to go, creates its own place.
July 8th, 2009 at 6:16 pm
Although the MARQ2 transit project referenced in the Minnesota link has been ridiculously disruptive to traffic (I am a perpetual pedestrian, ha) the delicate downtown district has not been upset by a city-wide reek of asphalt smell. I thank the Minnesota DOT, at least, for that.
July 8th, 2009 at 6:16 pm
Point special,
You’re right; we’re not talking about a closed system. Which is precisely why any heat energy reflected by a road can escape from the from the Earth’s environment.
Think of it like this: If you have a glass building and an asphalt road, the road will absorb almost all the energy incident upon it, as well as almost all of the light reflected onto it from the side of the glass building. If you replace the asphalt road with a concrete road, then not only will the road absorb less of the incident light, but it will absorb less reflected from the building, as well. Essentially, you’ve reducing the albedo of the road also lowers the albedo of the system as a whole.
Of course, the argument out there now is that the atmosphere now contains enough greenhouse gases that the Earth itself essentially has an albedo of 0, or something along those lines. In which, changing a road won’t change anything.
July 9th, 2009 at 2:50 am
The albedo of asphalt is really it’s main drawback as far as I am concerned. Not only does it absorb up to 95% of sunlight, but it also absorbs up to 95% of the light emitted by your headlights that strike it at night. Asphalt roads are nearly undrivable in a rain, with the lane markers and other on-road traffic controls rendered invisible under the glare of water reflections combined with the already dark road.
July 9th, 2009 at 1:24 pm
Have the researchers included the difference in manufacture of asphalt and cement? Asphalt is basically what’s left of petroleum after the gasoline, diesel, lubricating oil and other products have been removed. Cement involves baking powdered rock at 2600 degrees F for hours. Asphalt is mixed at about 375 degrees, and the new “warm mix” asphalts are mixed at 225 degrees.
As far as durability goes, concrete is harder and stronger, but tends to be less forgiving to both tires and repair crews when it does fail. One of the advantages of asphalt is the road can be opened to traffic as soon as it is cool enough to
I’m surprised that whitetopping wasn’t mentioned. This is a road rehabilitation method where the top few inches of older asphalt roads are milled off and replaced with four or more inches of Portland cement concrete.
July 9th, 2009 at 5:04 pm
[...] and photo from Infrastructurist by Jebediah [...]
July 10th, 2009 at 12:04 pm
[...] warming accord spells lifestyle changes [The Seattle Times] Walking the light rail line [Crosscut] It’s Time For Climate-Friendly Concrete Roads [The Infrastructurist] Cities Lose Out on Road Funds From Federal Stimulus [The New York [...]
July 11th, 2009 at 3:35 pm
How about we construct both?
July 15th, 2009 at 7:10 pm
[...] that if cities around the world “lightened up”–that is, made rooftops and paved surfaces more reflective–it would have the same effect as taking every car in existence off the roads [...]
July 30th, 2009 at 10:07 am
[...] My question is what would happen if we similarly painted all of our public (and private) transportation vehicles white or other light colors. The new Seattle light rail system (Sound Transit, see picture above) has the right idea with its fleet of white vehicles. Given how much space is covered with our vehicles I would have to imagine we would save a ton of energy by having white roofs on our cars, buses, trucks and trains, or other similar light colors. Perhaps we can just have the roofs of our vehicles white so that we still provide for colorful dynamics on the roads, which should also be whitened. [...]
September 21st, 2009 at 12:14 am
The concrete will be chosen so that when martial law comes, they can roll on it with tanks without cracking the asphalt.
October 13th, 2009 at 12:20 am
[...] which can be a hazard and nuisance to cyclists. If pervious concrete is used, it has the added advantage of reflecting more sunlight than asphalt, which can have a significant mitigating effect on climate [...]
January 14th, 2010 at 7:34 pm
Big problem though — concrete generates massive CO2 emissions during manufacture, due to the chemical processes involved in making “Portland cement”….
It appears that brick and cobblestone are actually the most climate-friendly (and also provide partly-permeable surfaces when installed correctly). Of course they’re only suitable for small local roads and streets, not high-speed roads.