"A team at Google's research arm used Google Maps to reroute a small portion of drivers in 10 U.S. cities,"
reports SFGate — including San Francisco and Los Angeles.
"Through their experiment, which was published
in the journal Nature Cities in June, the researchers sought to evenly spread traffic down more corridors as the drivers head to similar destinations, in the hopes of reducing congestion."
The experiments nudged up vehicle speeds by 2% on average on the congested roads, and shortened travel times by a modest 0.7%. Scientists have long thought that traffic could be eased this way, and this now demonstrates how it could actually work in the real world.
The researchers collected data on weekdays in the 10 cities, which included Seattle, Salt Lake City, Chicago and Atlanta. While they studied a variety of types of roads, from city streets to highways, they found that in cities such as Los Angeles where they targeted highways, their diversions had the biggest effect, with driving speeds in those areas increasing by about 4.6%. Most cities, though, saw a smaller improvement with speeds across them increasing by just 0.5% during peak times. The Google study's findings confirm what other researchers have long suspected, said Michael Manville, a professor of urban planning at UCLA who was not involved in the study. "This is a pretty nice empirical illustration of a longstanding idea," he said. If a clogged traffic artery is on the verge of a long delay, he said, rerouting a small number of vehicles away from the bottleneck produces a "not gigantic but noticeable result...."
As with other traffic interventions, there's a risk that Google's approach to spreading traffic could backfire. This concept, known as "induced demand," also applies to efforts like adding a lane to a critical highway, which temporarily relieves congestion, until traffic rises again. "You can do this, but you cannot be too successful, because if you are too successful, then more people will start driving, and essentially you'll be back to ground zero," [said Alexandre Bayen, a co-author of the study and director of UC Berkeley's Center for Information Technology Research in the Interest of Society]. "That's why when we did the study, we only operated at the margin." The idea is to make minor improvements, enough to matter in the aggregate but not so significant that people notice and start driving more, canceling those improvements...
The Google Research study also considered the potential environmental benefits of its traffic improvements. The paper highlights the carbon dioxide emission reductions resulting from the slightly smoother traffic flow and shortened travel times, which add up to a savings of about 1,000 metric tons annually. That's equivalent to the emissions of about 200 vehicles, a drop in the bucket for cities with millions of cars, the majority of which are still gas guzzlers, even in San Francisco and LA. Bayen acknowledges that while emphasizing the cumulative benefit if such efforts were sustained for a longer time. For Manville, the study is a useful proof of concept. "It is a demonstration that if we managed roads better, air would probably be cleaner," he said.
According to the article, "Google's study might not just be a one-off, and city officials could decide to make use of the Google research findings, Bayen said, such as by trying to improve traffic congestion on a larger scale..."
"Google declined SFGATE's requests for comment on whether the company informed city authorities or rerouted drivers about the study," the article points out.
