A driver hauling Taco Bell restaurant supplies in a big rig Monday morning from Napa to Petaluma ignored the large warning signs at the bottom of the steep and winding Oakville Grade.

Like many before him, he jackknifed the vehicle on a hairpin turn near the top and blocked the route between Napa Valley and Sonoma Valley, forcing lengthy detours for drivers. It took six hours to move the tractor and its 53‑foot trailer and reopen the road, according to a Napa CHP sergeant.

The driver admitted he’d seen the warning signs at the bottom of the Oakville Grade but “his GPS told him to take the route,” said CHP Sgt. William Bradshaw.

Multiple times a year moving trucks, big rigs and tourist buses get hung up on the curves along the 13-mile route snaking over the Mayacamas Mountains, connecting Napa Valley and Glen Ellen.

It’s not just an inconvenience for residents, say fire and law enforcement officials, but inhibits response times in cases of fire, crash or medical emergency.

“This shuts down the road. There was absolutely no way around this thing,” said Bradshaw, who helped supervise Monday’s clearing of the rig.

This one, a Transco Inc rig out of Danville, Illinois, got into trouble about 7:30 a.m. at the first of a couple of notorious turns near Trinity and Wall roads.

The trailer threatened to topple off the roadway and the effort to move it safely took three tow trucks, Bradshaw said. The driver was given a ticket for failing to obey the warning signs.

“The tow bills will be way worse than my little ticket,” Bradshaw said.

The rig was cleared about 1:30 p.m. But it didn’t take long, however, for a U-Haul driver pulling a trailer over the mountain to get hung up on the tight curves. It also had to be moved, Bradshaw said.

You can reach Staff Writer Randi Rossmann at 707‑521-5412 or randi.rossmann@pressdemocrat.com. On Twitter@rossmannreport.