Brent Saba had just dropped a church group off at Philadelphia International Airport yesterday morning and was heading north on Interstate 95 when it happened: His 15-passenger van ran out of gas.

Saba, a 24-year-old church pastor, made it to the shoulder just past the Ben Franklin Bridge and waited more than 30 minutes for someone to stop and lend him a cell phone. Then he waited a while longer for AAA to arrive with fuel.

With gas prices hovering at $4 a gallon, motorists are putting less fuel in their tanks - then coming up empty on the highway.

Though national statistics on out-of-gas motorists don't exist, there's plenty of anecdotal evidence that drivers are gambling by keeping their tanks extremely low on fuel.

In the Philadelphia area, calls from out-of-gas AAA members doubled between May 2007 and May 2008, from 81 to 161, the auto club reported. *