San Diego leads the nation in drunken driving, according to a new report from Insurance.com. The same source also ranked San Diego at the top of its list of 20 major metropolitan areas in 2010.

To assemble their list, the company took the number of people applying for insurance quotes through one of its websites, then determined the percentage that reported at least one alcohol-related violation.

The site is quick to note, however, that landing a spot near the top of its rankings doesn’t necessarily mean San Diego is home to more drunks in general — several factors could lead to increased convictions locally. A lack of a functional public transportation system and efficient or enforcement-heavy policing are both cited as reasons making it more likely that individuals will drink and drive or that they’ll be caught doing so.

San Diego also hosts a large number of out-of-towners, from vacationers to visiting businesspeople to members of the military, all of whom are cited by police officer Mark McCullough as potentially boosting the figures for local DUI arrests, though unless they applied for insurance using a San Diego address they wouldn’t have contributed to the survey rankings. “When you’re out of your element, your inhibitions run wild,” said McCullough, who coordinates DUI checkpoints for the San Diego Police Department.

Three California cities occupy the top five rankings, with Los Angeles coming in second and San Francisco fifth. San Jose, last year’s number two, dropped to seventh on the 2011 list.