Southern Californians appeared Saturday 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 the nation'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 freeways.

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 gotten 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 freeway's scheduled reopening early Monday.

"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.

Citizens clearly embraced the warnings, leaving neighborhood 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 freeway after police told him he couldn't do so, and one or more bicyclists also were intercepted on the route. Fajardo said officers now have orders to arrest anyone trying to enter the shuttered freeway.

Additionally, a suspected drunken driver was arrested after going around barricades to enter the freeway, 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.

Gail Standish, 47, peddled from Beverly Hills with her bicycling club to a 405 overlook a quarter-mile from the closed span.

"Everybody's calling this weekend Carmageddon, but seeing the freeway empty it feels more post-apocalyptic," Standish said.

Authorities looking at the potential impacts of the $1 billion interstate project spent months giving the public dire warnings. The event got its name when Los Angeles County Supervisor Zev Yaroslavsky told an early June press conference that "this doesn't need to be a Carmageddon" if people avoided driving.

Although no major delays related to the closure had occurred by midafternoon, a major test of was likely in the evening when Major League Soccer's Los Angeles Galaxy, featuring Britain's David Beckam, is scheduled to play Spanish heavyweight Real Madrid at Memorial Coliseum south of downtown.

One west side resident, David Noll, said he heeded the warnings and told his parents to cancel plans to come from the San Francisco Bay area for a visit.

"They made us believe that this weekend was going to be the worst thing ever, so I told my parents to stay home," he said. "I'm upset because we could have been hanging out together right now."

The potential for Carmageddon is rooted in Los Angeles' geography. The city is divided by the Santa Monica Mountains, which stretch more than 40 miles from near downtown westward through Malibu. The populous San Fernando Valley lies on the north side, and the Los Angeles Basin sprawls to the south.

Local and long-distance freeway traffic through the mountains has to squeeze through Sepulveda Pass on I-405 or about five miles to the east through Cahuenga Pass, which carries U.S. 101 through the heart of Hollywood. In between there is no grid of boulevards, just a few narrow, windy canyon roads.

Skirting the closure to the west of Sepulveda Pass would require even longer canyon routes between U.S. 101 and the Pacific Coast Highway.

The 405's load is increased by a major interchange with Interstate 10 below the south end of Sepulveda Pass and traffic associated with the University of California, Los Angeles, and Los Angeles International Airport.

At the north end of the pass, the 405 connects with U.S. 101, a major artery between Los Angeles and San Francisco. Farther north, the 405 also connects with the massive load of Interstate 5, California's backbone highway.

The drumbeat of "Carmageddon" warnings triggered an instant industry of businesses trying to capitalize on the phenomenon. JetBlue offered special flights from Burbank in the San Fernando Valley to Long Beach, with seats for the short hop costing just $4 or $5.

A cycling group saw that as an opportunity for a race. The cyclists started their ride 90 minutes before the flight's departure time to simulate the time that passengers would have to arrive at Burbank. Another member of the group took the flight and all were to meet at a Long Beach park.

Cyclist Stephan Andranian said it took the bikers one hour and 34 minutes to complete the ride from Burbank to Long Beach, largely following the Los Angeles River. Flight passenger Joe Anthony's total travel time including cab ride from Long Beach Airport to the park was just over 2 1/2 hours.

"We want to show that using a bike in LA is not only possible but that it can be faster than other modes of transportation," Andranian said.

Motorists, meanwhile, marveled at traffic conditions.

Tritia Nakamura found herself killing time at a drive-through coffee shop just off the 405 after allowing more time than usual to get from her home in Hollywood to West Los Angeles.

"The 10 was wide open, and I've never gotten here faster," said Nakamura, who noted she had seen so many Facebook postings about the clear roads that the situation could get bad if people decided it's OK to drive.

On-ramps to the 405 were shut down Friday evening, and the entire roadway was closed at midnight. Special deployments of police, firefighters, engines and ambulances were placed in the surrounding communities to ensure emergency services despite any gridlock. The UCLA Health System, which runs the huge Santa Monica-UCLA Medical Center near the 405, put its weekend staff in dorm rooms and hotels to ensure they don't run late to work.

Project contractor Kiewit Infrastructure West placed a 4-foot-high pad of dirt beneath the 80-foot-high Mulholland Bridge to protect the 405's surface from being damaged by falling concrete and steel.

Demolition work is expected to be completed by 2 a.m. Monday, followed by cleanup and reopening of the freeway at 6 a.m. Another 53-hour closure will be required in the future to demolish the north side of the span.

The existing bridge is 72 feet wide and 579 feet long. Caltrans says the new bridge will be 82 feet wide and 608 feet long with supporting columns relocated to allow construction of an additional freeway lane.