Skip to Content
Streetsblog USA home
Streetsblog USA home
Log In
Transit

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

3:41 PM EDT on September 28, 2015

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 spatial impact of transit in new ways [PDF]. Without transit, the researchers found, American cities would take up 37 percent more space.

Transit-oriented development in Portland's Pearl District. Photo: Smartgrowth.org
Transit-oriented development in Portland's Pearl District. Photo: Smartgrowth.org
Transit-oriented development in Portland's Pearl District. Photo: Smartgrowth.org

The research team from New York, San Francisco, and Salt Lake City modeled not just how many driving miles are directly averted by people riding transit, but how the availability of transit affects the way we build cities.

By allowing urban areas to be built more compactly, the "land use effect" of transit reduces driving much more than the substitution of car trips with transit trips. Total miles driven in American cities would be 8 percent higher without the land use effect of transit, the researchers concluded, compared to 2 percent higher if you forced everyone who rides transit to drive.

On average, the study found, the "land use effect" of transit is four times greater than the "ridership effect," or the substitution of car trips with transit trips. But the land use effect of transit varies a great deal across urban areas, the study found. In places like Greenville, South Carolina, it's responsible for reducing driving 3 percent. In San Francisco and New York City, it's 18 and 19 percent, respectively.

The authors suggest their model can help assess the effect of transit investments on travel behavior with greater sophistication. For example, adding a rail station to a neighborhood without one increased the density of jobs and residences by 9 percent within a one-mile radius, the study found. That would reduce driving about 2 percent for all the households across the area.

In addition to new infrastructure, increasing the frequency of transit service reduces traffic too. The researchers estimate that a 1 percent increase in transit frequency across a region would be expected to bring about a 0.045 percent decrease in miles driven. And a 1 percent increase in route density -- a measure of how many transit lines service a given area -- would be expected to produce a 0.047 percent reduction in traffic.

The report includes a "Land Use Benefit Calculator" [XLS] to help determine the total environmental benefits of transit projects.

Hat tip to Green City Blue Lake

Stay in touch

Sign up for our free newsletter

More from Streetsblog USA

Monday’s Headlines Drink Your Milkshake

How does a president end wasteful subsidies for the highly profitable fossil fuel industry? Many have tried, but none have succeeded, including Joe Biden.

March 18, 2024

How — and Why — To Start a Neighborhood E-Bike Library

American advocates are loaning out e-bikes to their neighbors — and creating flocks of new riders.

March 18, 2024

What Urbanists’ Doug Burgum Lovefest Reveals About the ‘Why’ Behind Our Advocacy

I am far less interested in talking about Gov. Doug Burgum's politics than talking about his values, and how those values shape his urbanism, and thus the actual lives of the people he governs.

March 15, 2024

‘Transit Hardship’: Report Shows Why Fair Fares Must Be Expanded to More Workers

A new report on transit fares has found that more than one-in-five moderate-income residents is “affordability hardship.”

March 15, 2024

Friday’s Headlines, Land Ho!

Transit agencies own a bunch of land, and some say they should sell it for housing to create more ridership.

March 15, 2024
See all posts