Reuters

Sure it makes travel easier. But that leads to more drivers on the road.

For years, progressive urbanists and environmentalists have advocated for synchronized traffic lights. Syncing lights, theoretically, makes everyone's lives easier: they promote a sense of flow and easiness on the road, and they reduce pollution, because a car running smoothly runs cleaner than a car stopping-and-starting.

So, the need to sync traffic lights has become somewhat well-known. The Baltimore Sun's transportation reporter wrote in 2010 that the "most common source of complaints" he heard from readers was out-of-sync lights. In 2011, a libertarian think tank praised Georgia's effort to syncronize lights, citing statistics about reduced drive times and gasoline usage. And sometime this year, according to an LA Daily News report, Los Angeles will complete its three decade-long effort to syncronize traffic signals across the city.

Except synchronizing traffic lights may not actually work. Todd Litman, of the Victoria Transport Policy Institute, writes in a recent post that efforts which increase flow, like signal-syncing or expanding-road-capacity, only theoretically reduce emissions:

[R]esearch suggests that at best these provide short-term reductions in energy use and emissions which are offset over the long-run due to Induced Travel. Field tests indicate that shifting from congested to uncongested traffic conditions significantly reduces pollution emissions, but traffic signal synchronization on congested roads provides little measurable benefit, and can increase emissions in some situations.

(I've stripped that quote of its citations.)

Why? Because if you make it easier and cheaper and faster for people to drive, more people drive. It's Jevons paradox, applied to the city -- if you make it more efficient to use a resource, more of that resource will get used.

There's a fun fallacy at work here. Changing the conditions of traffic flow changes the entire environment of the city. And re-creating conditions across the scope of a city which make one car more productive fail to account for the fact that, in a city, you're never just dealing with one car. You're not even dealing with one car many times. You're dealing with a whole environment of cars, and traffic-light-syncing, while it leads to many single cars having a faster trip, doesn't account - as a policy - for changes to the whole environment.

Photo credit: Eric Thayer/Reuters

This post originally appeared on The Atlantic.

About the Author

Most Popular

  1. Life

    The Cities Americans Want to Flee, and Where They Want to Go

    An Apartment List report reveals the cities apartment-hunters are targeting for their next move—and shows that tales of a California exodus may be overstated.

  2. photo: a pair of homes in Pittsburgh
    Equity

    The House Flippers of Pittsburgh Try a New Tactic

    As the city’s real estate market heats up, neighborhood groups say that cash investors use building code violations to encourage homeowners to sell.  

  3. photo: San Diego's Trolley
    Transportation

    Out of Darkness, Light Rail!

    In an era of austere federal funding for urban public transportation, light rail seemed to make sense. Did the little trains of the 1980s pull their own weight?

  4. Equity

    What ‘Livability’ Looks Like for Black Women

    Livability indexes can obscure the experiences of non-white people. CityLab analyzed the outcomes just for black women, for a different kind of ranking.

  5. Design

    Why Amsterdam’s Canal Houses Have Endured for 300 Years

    A different kind of wealth distribution in 17th-century Amsterdam paved the way for its quintessential home design.

×