BAKERSFIELD, Calif. — A man is dead following a single-vehicle crash on Highway 178 Tuesday morning leading to lane closures for several hours.

According to the California Highway Patrol, the crash happened just after 8 a.m. Tuesday morning on the 178 eastbound west of the Niles Street overpass. Authorities said the man was driving a Dodge Ram at about 60 to 65 miles per hour. The CHP said for an unknown reason the driver veered to the right off the roadway and struck a guardrail and collided head-on with the bridge overcrossing concrete wall. The driver was pinned inside the vehicle and died at the scene.

"For whatever reason, it left the roadway. It went onto the right shoulder to the dirt embankment and struck the Niles Street overcrossing wall without any breaking," explained CHP Officer Robert Rodriguez. "We don't know if this was possibly a medical emergency or if the driver fell asleep. That's still to be determined. This is definitely under investigation."

Lanes were closed for 2 hours during the investigation and clean up. Alcohol or drugs do not appear to be factors in this crash.