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Wednesday, Feb. 24, 2021

Is highway expansion effective at reducing traffic?

Rose Johnson, Gigafact
no

Research has shown that highway expansion “creates new demand for those lanes or roads”—a phenomenon known as induced demand. As a result, traffic congestion tends to remain about the same or worsen as more expansions encourage more people to begin driving.

In the 1960s, economist Anthony Downs created a new term for this: the law of peak-hour traffic congestion. It states that, “on urban commuter expressways, peak-hour traffic congestion rises to meet maximum capacity.” More recent studies have confirmed this law to varying degrees.

The Federal Highway Administration proposes other options for reducing traffic congestion. Among them: providing “street connectivity” or grade separations, adding high-occupancy vehicle lanes and adding capacity to other transit systems.

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