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.

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.

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.

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.

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.

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