Public Works Director Pete Ringen said the 150-foot zone is intended to provide a clear zone for recovery of disabled or errant vehicles.
Many county bridges have been constructed or improved with federal highway funds, which included features for a clear zone or recovery area to increase safety for the traveling public, he wrote in his report to the board.
"If people park along bridge approaches, that totally defeats the concept of the clear recovery zone," he said.
The zone will be marked with black and white signs saying "Emergency Parking Only."
"Therefore, a vehicle with mechanical or low fuel problems could remain in this area for a few hours until recovered by the owner or operator," Ringen told the commission.
The sheriff's department will have authority to enforce the parking.
The regulation will apply only to bridges on roads that qualify for federal funding for maintenance because of their traffic volume. This includes roads such as the Elochoman Valley and Altoona-Pillar Rock roads.