Southern Californians appeared to be willing to make the ultimate sacrifice to avoid the dreaded "Carmageddon" - leaving their cars in the garage.

Unusually light traffic flowed freely through America's second-largest city despite fears of epic traffic jams spawned by the 53-hour shutdown of a 10-mile stretch of one of the region's most critical roads.

Authorities closed the segment of Interstate 405 on the western side of the metropolis to allow partial demolition of a bridge, warning motorists to stay off the roads or plan alternate routes.

Officials were optimistic that the public far and wide had got the message, though there was some concern that the lack of gridlock would make the public complacent and that drivers would get behind the wheel before the road's scheduled reopening early tomorrow.

"We hope they still listen to what we're saying and not go out and try to drive through this area, because it is going to be congested if people do that," said Mike Miles, a district director of the California Department of Transportation, known as Caltrans.

Mayor Antonio Villaraigosa flew over the city in a helicopter and said it was clear there were far fewer cars on roads and streets than normal, but he cautioned at a mid-afternoon news conference that there were hours to go.

Citizens clearly embraced the warnings, leaving neighbourhood streets clear near the closure.

"It's been one of the most quiet Saturdays I've seen in forever," said Steven Ramada, who had expected to hear lots of cars honking in front of his Sherman Oaks home but instead only heard news helicopters.

"Everyone's calling this Carmageddon weekend, but it feels like copter-geddon over where we live," he said.

Not everyone was cooperating, though.

California Highway Patrol Officer Charmaine Fajardo said a 74-year-old man was arrested for jogging on the closed road after police told him he could not do so, and one or more bicyclists also were intercepted on the route. Ms Fajardo said officers now have orders to arrest anyone trying to enter the shuttered road.

Additionally, a suspected drunken driver was arrested after going around barricades to enter the road, Ms Fajardo said.

Progress on demolition of the half-century-old Mulholland Bridge was said to be good. Powerful machines with long booms hammered away at the south side of the span, which is being removed to allow the interstate to be widened. The plan is to leave the north-side lanes standing until the south side is rebuilt.

Authorities looking at the potential impacts of the one billion US dollar interstate project spent months giving the public dire warnings.