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Is Widening a Road a Good Way to Ease Traffic Congestion?

Last Modified Date: February 15, 2024

The next time you drive through road improvement work, be prepared to slow down -- even after the job is completed. That's because widening a road or adding lanes often increases congestion, according to an analysis of decades of traffic information.

Brown University economist Matthew Turner says the reason is that when people become aware of the supposed improvements to a roadway, they want to drive more; hence, traffic increases, and so does congestion. Turner cites the lengthy and expensive widening of I-405 in Los Angeles, which was completed in 2014. "The data shows that traffic is moving slightly slower now on 405 than before the widening," he said.

Due to the phenomenon of "induced demand," widening a highway will actually increase traffic congestion, as more people start to use the road.

Instead of unnecessary road work, Turner says the best remedy might be charging drivers in high-congestion areas. He argues that since roads are free, any improvements attract people -- a phenomenon known as induced demand -- but if you start asking people to pay to drive in certain areas, they'll stay at home.

Stuck in traffic:

On average, commuters in the United States sit in traffic for 54 hours per year.

Drivers in Bogota, Colombia and Rio de Janeiro, Brazil, face the worst congestion in the world, sitting in traffic for 191 and 190 hours per year, respectively.

According to Guinness World Records, the longest traffic jam in history stretched 108.7 miles (175 km) between Lyon and Paris in France on February 16, 1980.