July 16


I found the blog The Infrastructurist America Under Construction about a month ago.  They have a lot of interesting stuff.  Their current post is Stimulus Screws up Opportunity to Create Jobs, Save Energy.  It is about a company that paints rooftops white who can't get to the pot of stimulus money, even though their work lines up very well with the goals of the Obama administration (create jobs while reducing environmental impact).

The blog says, "Recent scientific work suggests 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 for more than decade and delay the progression
of global warming by approximately 20 years."

New concrete pavement has an albedo (a measure of reflectivity – the higher the number, the more reflective) of 0.55 while new asphalt pavement has an albedo of 0.04. Basically, concrete bounces sunlight back while asphalt absorbs it.

Historically, concrete pavement is more expensive to install than asphalt but it has a longer life cycle.  Asphalt used to beat concrete in the economic decision.  Maybe the environmental angle is the reason we should be using concrete instead of asphalt in roads and parking lots.  Or maybe we need to add white dye to asphalt….

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Mike Spack

My mission is to help traffic engineers, transportation planners, and other transportation professionals improve our world.

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