RIGBY, Idaho -

A man falling asleep at the wheel led to traffic being backed up on U.S. Highway 20 on Wednesday afternoon.

Idaho State Police said Jonas Karlinsey, 26, of Idaho Falls, was driving south on U.S. Highway 20 in a 2002 Toyota Corolla near Rigby when he fell asleep. He crossed through the median and entered the northbound lanes, striking a 2011 Ford F150.

The left northbound lane was partially blocked for about an hour and a half. Both drivers were wearing their seat belts.

Police did not give information on the drivers' conditions.

The crash is under investigation by the ISP.