By Joe Cortright, City Observatory
\nIncreasing road capacity to reduce greenhouse gas emissions will backfire
\nTime for another episode of City Observatory\u2019s Urban Myth Busters, which itself is an homage to the long-running Discovery Channel series \u201cMythbusters\u201d that featured co-hosts Adam Savage and Jamie Hyneman using something called \u201cscience\u201d to test whether commonly believed tropes were really true.
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\nToday\u2019s claim comes from the world of transportation. As we all know, transportation is now the single largest source of greenhouse gas emissions. Here, when confronted with the need to do something to address climate change, the highway lobby likes to point out that cars emit carbon, and when they\u2019re idling or driving in stop and go traffic, they may emit more carbon per mile than when they travel at a nice steady speed. And of course, they have a solution for that: spend more money expanding capacity so cars don\u2019t have to slow down so much. That\u2019ll be great for the environment, or so the argument goes.
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\nIn place of the now retired duo of Adam and Jamie, we\u2019ll turn this question over to Alex and Miguel\u2013Alex Bigazzi and Miguel Figliozzi, two transportation researchers at Portland State University. Their research shows that savings in emissions from idling can be more than offset by increased driving prompted by lower levels of congestion. The underlying problem is our old friend, induced demand: when you reduce congestion, people drive more, and the \u201cmore driving\u201d more than cancels out any savings from reduced idling.
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Urban myth busting: Congestion, idling, and carbon emissions<\/a><\/p><\/blockquote>\n