A woman riding a bicycle along San Francisco's Great Highway suffered serious injuries Tuesday evening, when she was struck by a driver.

According to the San Francisco Police Department, it was 7:17 p.m. Tuesday when the 23-year-old woman rode her bike near the intersection of Great Highway and Vicente Street.

(It's a bit confusing, but if you look at a map you'll see that there are actually two "Great Highway"s that are parallel to one another in that area — one which runs directly against Ocean Beach, and a second one that intersects with the east-west running streets in the area. The cyclist, according to police, was on this latter stretch of roadway.)

Police say that a "vehicle collided with bicyclist," but provided no information regarding the vehicle's presumable driver. Bay City News reports, however, that the driver was an 18-year-old man. According to SFPD, no arrests were made at the crash site.

The cyclist suffered "skull fractures" in the collision, police say. She was transported to San Francisco General Hospital for treatment of what police say are life-threatening "major head injuries."

BCN reports that the driver "remained at the scene" and that "drugs or alcohol do not appear to be factors in the crash." A call to police for more details on the circumstances of the crash was not returned at publication time.