A motorcyclist sustained serious head injuries Saturday when he collided with a sedan while attempting to change lanes.

The 21-year-old man, whose name hadn't been released, wasn't wearing a helmet. He was listed in critical condition, according to the Salt Lake County Sheriff's Office. A female passenger sustained minor injuries.

The accident happened on Highland Drive near 8000 South at 6:47 p.m. The sedan was apparently in the cyclist's blind spot, authorities said. Neither alcohol nor excessive speed were considered factors.