Some elevated and subway trains rolled through the evening rush hour yesterday, despite a strike by the city's transit workers. Ridership grew as word spread that trains were running and no fares were being collected.

"People seemed happy, and we're moving again," said Mayor Jane Byrne, who took a ride on a train and promised that service would improve today for the city's 1 million commuters.

Idle since Monday, some trains began running about 4 p.m. yesterday with few riders, possibly because the move had been announced only two hours earlier. Later, seats were filled and some passengers stood.

Union members predicted problems, but there were no reports of accidents.

Striking drivers and motormen were angry that supervsiors who are union members crossed their picket lines. "We'll remember this," said one of 11,000 striking union members.

Police said there were no reports of violence, but one train appeared to have been freshly spray-painted in an apparent act of vandalism, an officer said.

In announcing resumption of service, Eugene Barnes, chairman of the Chicago Transit Authority, said some union members as well as management personnel would help get the trains -- but not buses -- moving again. He said no fare would be collected initially "because of the inconvenience to our riders by the wildcat stoppage."

He said striking workers, who are defying a court order, were told they would be suspended if they did not leave picket lines and return to work.

Byrne ordered extra police protection, saying 170 police officers were assigned to trains, stations and "sensitive areas" in the city to protect trains and riders.