Los Angeles is bracing for "car-maggedon" next weekend when roadworks will close down a key stretch of freeway, in a city renowned for its traffic gridlock even at the best of times.

The work on the 405 freeway, which runs north-to-south near the Pacific coast, could notably snarl up traffic around Los Angeles' LAX international airport from Friday night to Monday morning.

The 405, or San Diego freeway, is one of the busiest freeways in the United States, and a key LA commuter hell-hole made famous when O.J. Simpson was followed live along it in a low-speed car chase in 1994.

From 7:00 pm Friday authorities will close a 10-mile section to replace a bridge on the highway, which takes up to 500,000 cars daily over the Sepulveda Pass through the Santa Monica mountains to the north of Los Angeles.

The closure will last for 53 hours until 5:00 am on Monday, with the building contractor threatened with fines of $72,000 per hour if the work is not finished on time for the Monday morning rush-hour.

"We based that on the cost of delay," said Mike Miles, an official from the California Department of Transportation (Caltrans), adding: "For every minute of delay, we figure there is a cost to the public."

For days Angelenos have been debating online and on radio phone-ins how to prepare for the feared monster gridlock, with some comparing it to the kind of traffic chaos brought by the 1984 Los Angeles summer Olympics.

Complicated alternatives to avoid the freeway - a key route between the sprawling LA basin and the San Fernando Valley to the north - are recommended. But some say the only real solution will be to avoid the area altogether.

"Stay the heck out of here," said Los Angeles County Supervisor Zev Yaroslavsky.