Transit Can Cut Car Traffic Much More Than Ridership Alone Suggests

Portland's Max Blue Line Light Rail helped reduce driving far more than its ridership numbers would suggest, a new study finds. Photo: TriNet
Portland’s MAX Blue light rail line helped reduce driving far more than you would expect based on ridership alone. Photo: TriMet

How much traffic does a transit line keep off the streets? Looking at ridership alone only tells part of the story, according a new study published in the Journal of the American Planning Association. The full impact of a transit line on motor vehicle traffic can far exceed the direct effect of substituting rail or bus trips for car trips.

Using data from the Portland region, University of Utah researchers Reid Ewing and Shima Hamidi compared self-reported travel in an area where a light rail line was built to an area that saw no transit investment.

The team collected data on changes in travel behavior in the area served by the MAX Blue light rail line and in the area around SW Pacific Highway. They compared stats from 1994 — before light rail was built — and 2011 — 13 years after it launched. They opted to use the 2011 data in order to show the full impact of denser, transit-oriented development around the stations.

Ewing and Hamidi found that light rail led to an average of 0.6 additional transit trips per day among each household in the surrounding community. By itself that would have cut total driving mileage by about a half mile per household per day — not a huge impact.

But the effect on driving among households living near light rail was much greater than that.

From 1994 to 2011, households in the area without new transit increased their driving by 62 percent (from 18.25 miles per day to 29.4), while households living near the new light rail line increased their driving only 22 percent (from 17.4 miles to 21.2).

Why was this effect so much larger than the effect directly attributable to new transit trips? Partly because households living near the light rail walked more and traveled shorter distances when they did drive. Walking increased 151 percent among people living in the transit-oriented communities, Ewing and Hamidi found.

That was possible because, following the addition of light rail, city, regional, and state agencies took steps to encourage walkable development around the transit line. And it worked. According to Ewing and Hamidi the “activity density” of the light-rail neighborhoods — a measure of how many households and jobs are located in a given area — rose 100 percent between 1994 and 2011.

The total driving mileage avoided by households living near transit amounted to three times the avoided mileage due solely to switching from driving to transit. Similar studies have estimated this “multiplier effect” to be in the range between 1.9 and 9.

  • mjcrites

    Thanks!

  • malachite2

    You could say the same about most of the US, given how the TBTF banks weren’t broken up, an updated Glass-Steagall bill wasn’t passed, nor were the banks in any real way penalized for their reckless and negligent activities. There have been some civil suits lately but I doubt if any damages awarded will equal the profits made during the bubble years.

    You’re right about Hillsboro though, it’s a town that loves its heavily subsidized airport. Aviation, particularly private aviation is heavily subsidized in Oregon, utilizing federal, state and local subsidies to function. If Hillsboro doesn’t continue to subsidize its airport (despite environmental and health costs to those living nearby), will it continue to flourish? What if aviation fuel costs go up more? I’m aware that there’s been some research in changing the composition of jet fuels to including other then fossil fuel components (to decrease soot & other pollutant production) but that won’t do much for all the small aircraft. Including the ones that use avgas or leaded fuel. There’s been some effort to introduce fuels w/less lead but it remains unknown how well that will go. Most other developed nations have phased out aircraft that requires leaded fuel.

    But if the subsidies end and big folks can’t fly their private jets everywhere they want to go will they stay? Or is Hillsboro just another “house of cards”?

ALSO ON STREETSBLOG

Without Transit, American Cities Would Take Up 37 Percent More Space

|
Even if you never set foot on a bus or a train, chances are transit is saving you time and money. The most obvious reason is that transit keeps cars off the road, but the full explanation is both less intuitive and more profound: Transit shrinks distances between destinations, putting everything within closer reach. A new study published by the Transportation Research Board quantifies […]

The Secrets of Successful Transit Projects — Revealed!

|
All across America, cities are investing in new transit lines. Which of these routes will make the biggest impact by attracting large numbers of new riders? A landmark report from a team of researchers with the University of California at Berkeley identifies the factors that set successful transit investments apart from the rest. The secret sauce is fairly […]
Chicago's Loop Link. Photo: Metropolitan Planning Council

Introducing a New Streetsblog Series: Getting Transit Right

|
With more American cities raising impressive sums to expand transit, the question of how to invest effectively is increasingly essential. So far, few places have hit on a policy combination that makes transit more useful to more people. To help cities "get transit right," Streetsblog is launching a new series about which transit strategies are working and which are not.

Economic Downturn Hits Transit Ridership — But Not in These Cities

|
The American Public Transportation Association (APTA) got the mainstream media’s attention during the holiday season after reporting that the dismal economy had helped push transit ridership down by 3.8 percent during the first three-quarters of 2009, when compared with the previous year. Ridership on L.A.’s heavy rail system grew by nearly 6 percent during the […]