DANVILLE -- A road-rage conflict between two vehicles devolved into a knock-down, drag-out brawl between two motorists on the side of a freeway Tuesday morning, the California Highway Patrol said.

The fracas began about 6:55 a.m. in southbound lanes of Interstate 680 near El Pintado Road when the drivers of a white Honda minivan and a black Toyota Camry "got in some sort of road-rage incident" with each other, said Officer Tom Maguire.

The vehicles collided in a glancing way, with both drivers believing the other initiated the collision, Maguire said. They both pulled over and started shoving, and the two tumbled down an embankment. The minivan driver, a 39-year-old man from St. Helena in Napa County, gained an advantage and repeatedly punched the face of the Camry driver, a 36-year-old Concord man.

Officers arrived and broke up the fight. Maguire said the CHP will pursue assault with a deadly weapon charges against both drivers for the collision and an assault complaint against the minivan driver who was considered the major aggressor.

An ambulance was summoned for the Camry driver but he refused medical attention.

Contact Robert Salonga at 925-943-8013.