A motorcycle rider and his passenger suffered serious head injuries after a crash on Highway 101, north of the Kastania Road exit, on Sunday night.

The 48-year-old rider, Victor G. Vaz of Petaluma, and his passenger, Vicki Tschirgi, 47, of Penngrove, were riding between cars at around 7 p.m. when they arrived in an area where traffic was slowed. A driver in a vehicle ahead of the 2006 Harley-Davidson motorcycle was starting to change lanes, but swerved back into the original lane after noticing that the motorcycle was coming at an unsafe speed, said Officer Jonathan Sloat of the California Highway patrol.

Vaz then overreacted, causing the bike to flip. Vaz and Tschirgi were thrown off the motorcycle, which landed upside down on its handlebars and seat.

Vaz and Tschirgi were taken to Santa Rosa Memorial Hospital for treatment of their serious head injuries.