OAKLAND, Calif. (AP) – San Francisco Bay area residents faced nightmarish commutes Monday after one of the region’s most traveled sections of freeway melted and collapsed following a fiery crash.

An elevated section of highway that carries motorists from the San Francisco-Oakland Bay Bridge to a number of freeways was destroyed early Sunday after heat from an overturned gasoline truck caused part of one overpass to crumple onto another.

“I’ve never seen anything like it,” said Officer Trent Cross of the California Highway Patrol. “I’m looking at this thinking, ‘Wow, no one died’ – that’s amazing. It’s just very fortunate.”

Authorities predicted the crash would cause the worst disruption for Bay Area commuters since a 1989 earthquake damaged the Bay Bridge itself. The sight of a soaring freeway twisted into a fractured mass of steel and concrete was reminiscent of the damage from the Loma Prieta quake.

Standing near the wreckage Sunday night, Governor Schwarzeneggerm Republican of California, vowed that the state would respond quickly to the damage.

Mr. Schwarzenegger declared a state of emergency to speed up cleanup and rebuilding efforts. He also authorized free transit Monday on ferries, buses and the rail system that takes commuters across the bay.

Transportation officials said it could take months to repair the damaged interchanges, and advised motorists to use public transportation in and out of San Francisco. They added trains to the rail system and said drivers who chose to take alternate routes Monday would still face tough commutes.

“People are going to have to find a different way to work and back home in the evening, so we are asking them to plan ahead and do their homework,” said Jeff Weiss, spokesman for the California Department of Transportation. “This isn’t going to be fixed in a matter of days.”

Nearly 75,000 vehicles used the portion of the road every day. But because the accident occurred where three highways converge, authorities said it could cause commuting problems for hundreds of thousands of people. State transportation officials said 280,000 commuters take the Bay Bridge into San Francisco each day.

Though heat from the fire was intense enough to weaken the freeway and damage a 250-foot stretch of highway, the truck’s driver walked away from the scene with second-degree burns.

James Mosqueda, 51, of Woodland, went to a gas station and called a taxi, which took him to a hospital, Mr, Cross said.

A preliminary investigation indicated Mosqueda may have been speeding on the curving road, he said. Mr. Mosqueda was being treated in a hospital for burns on Sunday; efforts to reach him there were unsuccessful.

He was headed from a refinery in Benicia to a gas station near the Oakland airport when the accident occurred, according to the patrol.

The crash occurred around 3:45 a.m. on the MacArthur Maze, a network of ramps and interchanges at the edge of downtown Oakland and about a half-mile from the Bay Bridge toll plaza. Witnesses reported flames rising up to 200 feet into the air.

Heat exceeded 2,750 degrees and caused the steel beams holding up the interchange from eastbound I-80 to eastbound Interstate 580 above to buckle and bolts holding the structure together to melt, leading to the collapse, California Department of Transportation director Will Kempton said.

The cost of the repairs would likely run into the tens of millions of dollars, and the state was seeking federal disaster aid, Mr. Kempton said.

Officials said the accident could have been deadly had it occurred at a busier time.

San Francisco Mayor Gavin Newsom said the accident showed how fragile the Bay Area’s transportation network is, whether to an earthquake or terrorist attack.

“It’s another giant wake-up call,” Mr. Newsom said.

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Associated Press writer Tom Verdin in San Diego contributed to this report.