A Nebraska sheriff's deputy jumped into the cab of a runaway semitrailer after the driver apparently passed out at the wheel, stopping the vehicle from possibly crashing off a busy viaduct bridge.

Deputies responding to a 911 call about a reckless semi on U.S. Highway 81 caught up with the truck in Madison County, but it wouldn't stop.

The truck slowed as it neared Norfolk, 110 miles northwest of Omaha, allowing Deputy Todd Volk to leap into action. He jumped from a cruiser onto the highway, then into the truck's cab, where he was able to stop the big rig on the bridge.

Volk says the driver appeared to be sick and officials said it may have been a diabetic reaction.

Radio station KNEN in Norfolk says the incident happened Dec. 2.