The draft report looked at trends associated with 40,000 mortgages in San Francisco, Chicago and Jacksonville, Fla. The release date for the final study has not been announced.

The research included borrowers’ income and expenses, credit scores and loan-to-home value ratio.

It focused on the average number of vehicles owned per household in a neighborhood, and through a complex formula, found that the likelihood of mortgage foreclosure increased as neighborhood vehicle ownership rates rose.

“In the same way that better credit risks, more disposable income and other factors are taken into account, locations that are in more mass-transit and walkable communities should be a key consideration in how mortgage underwriting takes place,” said Chris Leinberger, a real estate professor at the University of Michigan, who is a proponent of the study’s findings.

The study notes that transportation costs, including gasoline, are roughly 17 percent of the average American household’s income – about $8,750 per year – but that standard lending practices give them far less consideration.

Bay Area real estate agents and loan brokers said it makes sense for lenders to take into account transportation costs along with other debt carried by borrowers.

“Transportation could be a major contributor to a buyer’s ability to pay off their loans every month,” said Glenn Bell, an East Bay real estate agent.

Bell noted that many of the Bay Area neighborhoods that experienced high foreclosure rates in the past two years were in outlying areas, such as Tracy and Stockton, where residents commuted long distances to work.

The strategy of traveling to the far suburbs to find desirable, affordable housing backfired when gas prices spiked, he said.

Some lending industry observers said it is logical that transportation costs affect people’s ability to pay their mortgage. But other factors, such as risky lending and unemployment, have a much more direct impact.

Some areas with relatively efficient public transportation and low car ownership rates in the inner-city Bay Area have seen high foreclosure rates, according to Paul Leonard, the Center for Responsible Lending’s Oakland office director.

“I have to imagine that a dramatic increase in gas prices would impact the ability to pay loans for people who have long commutes,” Leonard said. “But East and West Oakland, as well as suburbs like Antioch and Pittsburg, have had high levels of foreclosures.”

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