Saturday, July 05, 2008

Density and Public Transportation

Many recent news stories have noted that more Americans are switching to public transportation because of higher fuel prices. Over the past six months, Americans have driven 30 million fewer miles; meanwhile, ridership on public transit is at its highest level in 50 years. This article suggests some caveats.

Most of America's public transit riders are based in a few large cities. About half of all transit commuters live in Baltimore, Boston, Chicago, Houston, Los Angeles, New York, Philadelphia, San Francisco, Seattle and Washington, according to the Congressional Research Service. Collectively, these cities and surrounding areas make up roughly 70 percent of all public transportation trips in the United States.

That's not surprising, since public transportation works best in areas with at least 15 homes per acre and preferably more, Deakin said. America's love for low-density housing development makes mass transit less feasible in areas without large urban cores.

If a half-mile radius is the maximum convenient walking distance for a transit station, 7,800 workers would reside in the estimated 400 developed acres encompassing that half-mile radius, Deakin estimates. "If 25 percent take transit to get to work, that is only 2,000 transit commuters, a pretty low number for the transit station ... and work trips tend to be half of all trips made by transit," Deakin said.

"Bottom line: We can get people to select transit when it is convenient, comfortable and a good choice, but if we build all low-density neighborhoods, few people will have a reasonable transit option," Deakin said.
It is true that most Americans do not have access to good public transit – a fact that has made the current surge in gas prices so painful. This deficiency ought to be remedied as quickly as possible. Moving more commuters from cars to transit would ameliorate the effects of higher fuel costs and reduce the overall contribution of transportation to climate change. Building new transit lines, especially rail, would create opportunities to build higher-density neighborhoods and reduce the need to destroy wildlife habitat for building new subdivisions and shopping centers.