One million bus and subway commuters awoke to a surprise walkout of municipal transit workers this frosty morning, eight days after Mayor Jane Byrne assured them the city had averted a strike.

Bundled up against subfreezing temperatures and a wind chill factor of minus 20, many commuters unaware of the strike waited in vain for buses and trains that never came.

Defying a court injunction, 11,000 members of the Amalgamated Transit Union walked off the job at 3 a.m. today. They had been working without a contract since Dec. 1.

One historian said it was the first municipal strike in the city's history.

John M. Weatherspoon, head of the bus drivers local, said the strike was called "because of the attitude of the Chicago Transit Authority. . . ."

The walkout snarled downtown streets and expressways as CTA riders sought ways of getting to work. As the morning rush hour continued into midday, some who drove to work reported their trips had taken five times longer than usual.

Adding to the problem was a Teamsters Union walkout against seven major oil companies that caused a growing shortage of gasoline in the city. Long lines in many service stations were reported as the transit strike increased gasoline consumption.

Taking a hard line at a morning news conference, Mayor Byrne said she had no intention of calling both sides into her office for round-the-clock bargaining sessions as had been the practice of previous city administrations.

"I could invite anybody in and give the city away," Bryne said. "But I won't do it."

A CTA spokesman said supervisory personnel could not run the system. "We just don't have enough people to make the service worthwhile," he said.

Little more than a week ago, Byrne said agreement had been reached with the transit union on what was believed to be the major issue in the negotiations -- the cost of living adjustment (COLA) in the contract of drivers, whose current $10.58 hourly wages are the highest in the continental United States.

"The COLA has been resolved," Byrne had said. "There will be no work stoppage."

But Byrne apparently had spoken too soon. Rank-and-file members reportedly were upset by the COLA settlement their union had reached with the city. Byrne said the union had reneged on the deal.

In response to the strike, the mayor lifted normal parking restrictions in the Loop and asked citizens to help each other get to work.

In addition, suburban rail systems added trains and shuttle service to help CTA commuters living near suburban stations.

William Adelman, labor historian at the Chicago Circle campus of the University of Illinois, said the transit strike was the first against municipal government in the city's history.

Asked by a caller to verify some other information, Adelman said, "I'd like to, but I'm the only one in the whole department to make it to work."

Absenteeism was believed to be high and downtown offices, and many retailers reported a decline in business during the usually hectic week before Christmas.

CTA director Eugene Barnes said he would try to have union leaders arrested if they continued to disobey the temporary restraining order the authority obtained Sunday evening from a Circuit Court judge.

A court hearing on the restraining order was scheduled for Wednesday morning.