A man was critically injured Saturday night when the four-wheeler he was riding crashed on Highway 8 near the county line.The victim, Caleb Wolfe III, 52, was airlifted from the scene to Erlanger Medical Center in Chattanooga. According to Highway Patrolman Brent Collier, the wreck happened around 9 p.m. Saturday atop Harrison Ferry Mountain on Highway 8 within a couple of miles of the Warren-Van Buren County line.Collier said an investigation of the scene showed Wolfe was traveling toward Chattanooga (away from McMinnville) on Highway 8 when he crashed and overturned. He was not wearing a helmet and his head hit the pavement causing the serious injuries that prompted his airlift from the scene.The trooper said the cause of the wreck is still under investigation as lawmen are trying to determine if he was struck by a vehicle or if he lost control of his ATV. He was the driver and sole occupant of the four-wheeler.