Commuters Stranded by Transit Strike : MTA: Talks with mechanics union break down. Drivers union reaches tentative pact but agrees to honor picket lines.

A strike against Los Angeles County’s Metropolitan Transportation Authority began this morning, after contract negotiations between the MTA and the mechanics’ union ended, an MTA spokeswoman said.

Although the drivers’ union reached tentative accord and the clerks’ union was nearing an agreement late Sunday, the mechanics’ union failed to resolve its differences with the MTA, and talks broke off shortly before the midnight strike deadline, officials said.

The labor dispute, the first in a dozen years, could strand as many as 1.2 million riders and create a traffic Sig-Alert for everybody else.

It is the first shutdown of the nation’s second-largest transit system since 1982, when drivers walked off their job for five days, and would provide a double whammy to bus and train riders who two weeks ago were hit with a fare increase. There was a 68-day walkout in 1974.

Contracts between unions representing 6,500 bus and train drivers, mechanics and clerks expired June 30.

A spokesman for Gov. Pete Wilson said Sunday that the governor will not seek an order imposing a 60-day cooling-off period.

A Wilson aide pointed out that both Democrats and Republicans on the MTA board had unanimously asked Wilson not to intercede, in an apparent tactic to pressure the unions to reach a settlement. The bus drivers union has asked Wilson to intervene.

But it also benefits Wilson politically not to intervene, transit officials said. For the governor, it would be better to have a strike now rather than closer to the November election, when it would be fresher in voters’ minds. Wilson has said that he is concerned that delaying a strike until September would hit students returning to school.

During a strike, the MTA plans to operate about 300 buses on the 30 busiest routes--a mix of MTA buses operated by non-union workers and yellow school buses driven by drivers from private companies. (Usually, the MTA operates 1,900 buses on 200 routes.) MTA is paying $160,000 a day to contract with two private bus companies.

Service on the Blue Line and the Red Line subway would continue. Bus and train service would operate only from 6 a.m. to 6 p.m. weekdays.

The fare on MTA buses and the Metro Blue Line would be 50 cents during a strike, with no transfers. Elderly and disabled would pay 25 cents. Fare on the Red Line would remain 25 cents. No fee would be charged to board the private school buses during at least the first week of the walkout. Once fare boxes were installed, the fares would be the same as other strike fares.

“Driver qualifications and maintenance standards for MTA buses and trains during a strike will not be compromised,” said Franklin White, MTA’s chief executive officer.

Initially, MTA replacement drivers would be supervisors who once drove buses. But the MTA is training other workers to drive buses if the strike drags on.

Unlike transit workers in some East Coast cities, California bus and train operators are not prohibited from striking.

A strike would not include the Metrolink commuter rail or municipal or private operators such as the Los Angeles city commuter express and DASH shuttle buses, the Long Beach, Montebello and Santa Monica municipal lines and Foothill Transit.

Metrolink plans to increase train service during a strike. Officials also plan to modify the routes of the DASH shuttle and commuter express lines to link up to MTA buses in the event of a strike.

Robert Yates, head of the Los Angeles Department of Transportation, said he will be monitoring traffic conditions on a computer in City Hall and assign 500 traffic control officers as needed to congested intersections. A special team of traffic engineers, who put together traffic-easing measures during the 1984 Olympics and January earthquake, also was standing by.

The transit workers were set to strike last Monday but delayed the walkout for a week after Mayor Richard Riordan and other top transit officials agreed to meet with union leaders.

The big sticking point has been proposed changes in work rules and contracting. The agency wants to turn over some bus lines to private operators, cut back on drivers’ overtime and reduce the MTA contribution to health benefits.

Union members say contracting will eliminate some jobs. Terms of the agreement were not revealed.

Information is available to commuters at 1-800-COMMUTE. For Metrolink: 1-800-371-LINK.

Times staff writer Duke Helfand contributed to this story.