A file photo shows the parking lot at the New Carrollton Metro station. A new study says land near transit stations is so valuable that less of it should be used for parking. The study also found that cities and suburbs often require too much parking near transit stations, leaving parking lots and garages underused. (Photo by Linda Davidson / The Washington Post)

Auto-centric standards and zoning requirements have led to too much parking being built around transit stations, leaving many parking spaces empty and wasting valuable land that could be better used, according to a study released Tuesday by Smart Growth America.

The study, which is also published in two peer-reviewed journals, found that in some cases, about one-third of the parking spaces that would be recommended for a new development under industry standards were actually used, even at peak times.

None of the five transit-oriented developments studied — in Washington, Los Angeles and Oakland, and near Seattle and Denver —  generated enough parking to fill even half the number that planning industry standards would have suggested, the study found. The developments reviewed actually included fewer parking spaces than those standards recommended. Even so, they still had between 16 percent and 42 percent of their parking spaces empty at peak times.

“This shows the traditional views of parking should be thrown out the window when you look at transit as a major component of a development,” said Harold Stitt, a senior planner in Englewood, Colo., which has one of the developments included in the study. Stitt spoke as part of a webinar that Smart Growth America hosted to explain the study.

Urban planners have long suspected, and studies have shown, that the amount of parking available is a key factor in how many people drive, as well as how often and how far they’ll drive. Many planners, particularly in urbanizing suburbs that are beginning to focus growth around new transit stations, are re-examining the amount of parking required under their own auto-centric zoning codes and recommended under guidelines from the Institute of Transportation Engineers.

The study authors said those industry guidelines for estimating the number of vehicle trips a new building would generate and the amount of parking it would need were based on development in more isolated, auto-centric suburbs.

The study found that in Washington’s Rhode Island Row development adjacent to the Rhode Island Avenue Metro station, about 64 percent of the parking spaces were occupied, even at peak times. If that development had the number of spaces suggested under the industry guidelines, only 33 percent of the spaces would be used. A transit-oriented development in the Koreatown neighborhood of Los Angeles had similar percentages of parking capacity then went unused, the study found.

“This confirms what we theoretically and anecdotally understood,” said Patricia Diefenderfer, a senior city planner in Los Angeles, who participated in the webinar about the study’s findings.

Because people’s proximity to transit is critical to how likely they are to use it, the land within one-quarter to a half-mile of transit stations is particularly valuable and could be better used housing people, office space or retail rather than cars, the study found. Parking lots and garages around transit stations also makes them more difficult to walk and bike to, experts say.

“The land close to stations is most valuable,” said Chris Zimmerman, Smart Growth America’s vice president for economic development and a former Arlington County board member. “Every foot matters.”

In addition to being inefficient, requiring developers to build excess parking, particularly relatively pricey garage parking, makes living near transit more expensive and makes such projects less financially viable for developers, the study said. The demand for homes within walking distance of transit, including in suburbs, far outstrips the supply, which makes them less affordable.