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Comment by pragmatic | Hacker News Reader

A real innovation would be material that turned white/reflective in hot weather and black in cold weather.

Heat is only a concern half the year in temperate climates. The other half is severe cold. (Think 90F and 90% humidity in summer and 0F in Winter (makes you wonder why we live here, doesn't it?)).

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Done and done http://www.inventables.com/technologies/heat-reactive-paint

But given that dark colors also radiate heat, wouldn't the white be better year round anyways?

Dark coloured surfaces will tend to absorb more heat. You want that in the winter to help melt snow and ice.

When there is snow and ice on the road the surface will is light colored (white or grey).

Dark surfaces radiate the minimum amount of heat, though. A perfectly black body will absorb all incoming radiation and re-emit it back by a Boltzmann distribution (according to its temperature). Less than perfect surfaces would reflect some the incident light/heat; if they reflect at the same constant or regular angle, we recognize it as 'shiny', while if it's a random angle, our eyes recognize it as matte/solid white.

While you are correct, in the case of dark pavement with patches of snow lying on top, conduction will be a far more prominent transfer mode than radiation.

(Although neither will be really large, and I think the blinding effect from a light pavement would be a more important issue here.)

Except it won't absorb anything if the snow reflects all of the light.

It makes sense to absorb heat when there is little or no snow, but it doesn't at all when snow covers all of the surface.

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