Building More Roads Leads to More Traffic

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Image: Michael Gil via flickr

Here at TreeHugger, we talk quite a bit about the causes and problems with roads and traffic, and we've seen how effective congestion pricing can be. Here's one more study showing that more roads are not the answer to our rush hour traffic problems: they only attract more cars.NPR reported on the study as LA was gearing up to close 10 miles of Interstate 405 for the weekend to allow for the latest phase of a $1 billion widening project.

But University of Toronto researchers found that instead of providing relief for existing traffic, widening and building more roads leads directly to more traffic:

"What we found was that in cities where there was more roads, there was more driving," economist Matthew Turner, a co-author of the study, tells weekends on All Things Considered host Guy Raz. "In particular, if you had 1 percent more roads, you had 1 percent more driving in those cities."

Changes in public transportation, however, had no effect on traffic, according to the study—riders will fill newly-created space on buses and trains, but traffic congestion will remain the same. Turner told NPR that's because: "As you add roads to a city those roads get filled up. There are people waiting to use that capacity. The result on transit is almost exactly the opposite of that."

The only legitimately effective solution, according to the team's research, is congestion pricing, a tactic that has already helped cities like London, Singapore and Stockholm. Congestion pricing in Stockholm, for example, has cut travel time in half, and carbon dioxide emissions by 18 percent, during peak hours.

More on roads and congestion:
Congestion Charge Cuts Waiting Time 50% and CO2 by 18% in Stockholm
Mapping Traffic Pollution Sends MESSAGE Loud and Clear
Walking: An Equal-Opportunity Answer to Traffic Congestion, From New York to New Delhi

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