An off-duty Marietta police officer was seriously injured Friday when a motorcycle he was riding collided with a car on Dallas Highway in Cobb County, authorities said.

Officer Michael Randall was riding alone and heading home on his Kawasaki ZX10R motorcycle, westbound on Dallas Highway approaching Garrison Commons Drive NW, shortly before 9 a.m. when the accident occurred, police said.

A black 1995 Volvo driven by an unidentified woman and coming the other direction apparently turned left onto Garrison Commons and into Randall’s path, police said. The two vehicles crashed.

The 31-year-old Randall, a six-year veteran of the Marietta department, sustained serious injuries, including multiple broken bones.

“He was wearing a helmet, which saved his life, but obviously, there’s still the threat of potentially other injuries. He’s in the hospital in the ICU right now,” Marietta police Officer David Baldwin told The Atlanta Journal-Constitution.

Randall was taken by ambulance to Wellstar Kennestone Hospital, Marietta, where he was listed in critical but stable condition Friday afternoon, Baldwin said.

The Volvo’s driver was alone in her vehicle and was not injured, Sgt. Dana Pierce of the Cobb County Police Department told the AJC. An accident investigation was under way, and no citations had been issued as of Friday afternoon.

Pierce said drivers of cars and bikes need to be alert for each other – especially when turning into oncoming traffic.

“People turning left need to understand a motorcycle will close on them quicker than the motorcycle driver might imagine and certainly quicker than the driver of the automobile may imagine,” Pierce said.

“It really is an optical illusion because the smaller person on the motorcycle appears to be farther down the road,” he said. “The person in the car feels they have time to get off the main roadway or pull out of a driveway or secondary roadway … [yet] the time for the vehicle driver to get out of the way is reduced drastically. And that’s compounded by the speed of the motorcycle.”