A Cheyenne man is dead following a Wednesday evening crash on Interstate 80.

Wyoming Highway Patrol Sgt. Kyle McKay says 58-year-old Mark Greene was headed eastbound near Buford when, for reasons unknown, he drifted off the road, striking a highway post sign and then a guardrail.

"The vehicle rode the guardrail, continued across the grassy gore and then hit a fence whereupon it became airborne and landed on the backside of west Remount Road," said McKay.

"It struck the guardrail, crossed Remount Road and then struck the east guardrail face and a highway sign," he added. "The vehicle came to rest facing north on its wheels against the east Remount Road guardrail."

Greene, who was restrained in a motorized wheelchair, was thrown out of his chair, but remained inside the vehicle.

McKay says an investigation is ongoing to determine if Greene suffered a medical condition prior to the crash.