A bicyclist was seriously injured Sunday afternoon after she attempted to ride across Mendocino Avenue in a crosswalk near Santa Rosa Junior College and was struck by a sport utility vehicle, witnesses said.

The woman's identity was not immediately available. She was loaded into an ambulance after the 3:30 p.m. crash and taken to a hospital with what appeared to be a broken leg.

Cathy Griffice of Santa Rosa said she was stopped in a southbound turn lane at the intersection of Mendocino and Pacific Avenue when she watched the woman ride into the crosswalk heading toward the junior college.

Griffice, who was behind the wheel of a Chevy Trailblazer with a 17-foot trailer attached to it, said the bicyclist had made it about 10 feet across the intersection when the lights on Mendocino turned green for southbound traffic.

Griffice said the woman appeared to realize she was in danger as she rode past the Trailblazer and was struck by a Toyota Land Cruiser.

"There was silence, and then all of a sudden she started screaming," Griffice said.

The Toyota's driver, 17-year-old Dylan Gerard of Upper Lake, said he had no time to avoid the collision. He estimated his speed at about 30 mph.

"It was a solid green light, and then suddenly, she was there," said a visibly shaken Gerard. He said he was on his way to meet friends for an afternoon of swimming.

Sam Marsi, who had been smoking a cigarette outside the Wash World Laundromat, described the crash as an "explosion of glass."

He said he found the woman lying in the roadway with what looked to him like a broken leg. Her rust-colored Schwinn Suburban was crumpled beneath the Land Cruiser. One of the vehicle's headlights was shattered.

Witnesses said the cyclist was not wearing a helmet.

Santa Rosa officers investigated the crash along with junior college police.