Whenever gasoline prices in the United States spike, some people flip over to mass transit. Bus and subway ridership goes up. But most Americans can’t easily make this switch. And a new Brookings report (pdf) explains why: Most major transit systems in the United States don’t do a very good job of bridging the gap between where people live and where they work.

(Dana Hedgpeth/Washington Post)

As it turns out, most jobs within major metropolitan areas are accessible by transit. “Over three-quarters of all jobs in the 100 largest metropolitan areas are in neighborhoods with transit service,” the report notes. Access is better in cities in the Northeast and West than in the South. And urban jobs are far more accessible than suburban jobs. But overall, there are some 77.7 million jobs nationwide that are near a bus or train line.

The problem? Most people don’t live within easy reach of those lines. “The typical job,” author Adie Tomer writes, “is accessible to only about 27 percent of its metropolitan workforce by transit in 90 minutes or less.” Even though millions of people live near transit stops, and even though millions of jobs are near transit stops, those systems don’t line up in a way that allows most people to commute by mass transit in less than 90 minutes.

This is primarily a reflection of the fact that, for decades, both people and jobs have been moving from inner-city areas (which tend to be more transit-accessible) to suburban areas. About 63 percent of jobs in the country’s 100 biggest metropolitan areas are now located in the suburbs. And most people now reside in the suburbs. Matching up those locations can be tough.

And many cities have not kept up. For instance, in the New York City-New Jersey-Long Island metro area, the typical job is transit-accessible to 58.4 percent of the urban population. But that typical job is only transit-accessible to 14.4 percent of the suburban population. For that reason, the New York metro area ranks surprisingly low in Brookings’ overall metro rankings — 17th in the country  — despite its extensive subway system. (The Wall Street Journal’s Conor Dougherty has compiled a handy list here.)

Some cities, however, have done somewhat better. The report notes that jobs in Utah’s metro areas seem to have a high level of transit accessibility, particularly in Salt Lake City (64.1 percent), but also in Provo (47 percent) and Odgen (44 percent). That’s because those areas have focused on extending their transit links out to suburban neighborhoods.

Of course, a lack of transit accessibility isn’t fatal to a city. Most workers in the country do drive, after all. However, Tomer notes, there are several reasons why cities may want to boost transit accessibility. For one, commutes are getting longer and longer, stretching from 9.9 miles, on average, in 1983 to 13.3 miles in 1999. Americans now waste 34 hours a year, on average, sitting in traffic jams. And the cost of car ownership has gone up, especially when gas prices surge. Because of that, roughly 10 percent of workers in the biggest metro areas don’t even own a car — particularly in low-income households.

For all those reasons, the report notes, some cities like Denver and Hartford are currently trying to upgrade their systems by matching employment centers with multiple regional neighborhoods. Other suburban areas like Tyson’s Corner, Va., meanwhile, are slowly in the process of transforming into denser, more accessible areas that are less dependent on automobiles. But the process is still quite slow.