Nicolay Pokornyy, 63, of Walnut Creek, was driving north in a full-size GMC van at 60 mph on the highway when the van drifted to the right shoulder and struck the cyclist, CHP Officer Jon Sloat said.
The accident happened at 7:24 a.m. south of Kastania Road south of Petaluma where bicyclists and pedestrians are allowed on the shoulder of the highway, Sloat said.
Pokornyy said he was trying to determine where his exit was when the van drifted onto the shoulder, Sloat said.
The bicyclist was taken to Santa Rosa Memorial Hospital and is not being identified until his family can be contacted due to the severity of his injuries, Sloat said.
Alcohol is not considered a factor in the collision, Sloat said.