A confrontation between a motorist and a pair of cyclists vying for space on a rural Marin County road ended with the driver ramming the rear wheel of one of the bikes, ejecting the rider, CHP officials said.

CHP Officer Andrew Barclay said investigators suspect the driver intentionally rammed the cyclist, a San Francisco man who escaped serious injury and declined medical treatment. Driver Mark Rafferty, 62, of Bolinas was arrested on suspicion of assault with a deadly weapon, Barclay said.

The encounter began at about 1:10 p.m. Monday on Point Reyes-Petaluma Road west of Nicasio Valley Road, a bucolic area of rolling hills and pastures popular with cyclists.

Two bicyclists including Charles Keane-Zirepolo, 25, of San Francisco were heading east when one of the riders drifted into the eastbound lane, according to Barclay. Rafferty was also heading east, and began honking his horn as he approached the cyclists from behind in a green Saturn sedan, the CHP said.

As Rafferty tried to pass the cyclists, one of the bikers veered left and blocked his path, forcing Rafferty to hit the brakes to avoid a collision, according to Barclay.

Rafferty then drove ahead, pulled over, exited the car and “yelled at Keane-Zirepolo to come to his location so he could express his disapproval for how he was riding,” Barclay said.

Keane-Zirepolo did not stop, displaying an “obscene hand gesture” as he passed Rafferty, then pedaled ahead to catch up with his cycling mate, according to the CHP.

Rafferty then got back into his car and accelerated toward Keane-Zirepolo, who was at this point cycling on the right-hand shoulder, CHP officials said.

Rafferty drove into the rear wheel of Keane-Zirepolo’s bike, crushing the wheel and ejecting the rider from the bike onto a dirt hillside, Barclay said.

Rafferty drove away, heading east on Point Reyes-Petaluma Road but then turned around and drove back to the scene, the CHP said.

Officers interviewed all parties involved as well as an independent witness.

You can reach Staff Writer Julie Johnson at 521-5220 or julie.johnson@pressdemocrat.com. On Twitter @jjpressdem.