BOSTON, DEC. 31 -- Transportation officials today admitted error in a trolley car accident that injured 33 people last week and said they had fired a driver whose blood-alcohol level tested above the legal limit.

The Massachusetts Bay Transportation Authority (MBTA) will start testing its employees at random for alcohol and drugs in the wake of the Friday morning accident, MBTA officials said.

Two dispatchers who allegedly were slow to react to a passenger's warning about the driver's behavior that morning have been reassigned, they said.

"We dropped the ball," Thomas P. Glynn, the MBTA's general manager, said at a news conference. "We did not act in time to avert this accident."

A test after the accident showed the driver, whom authorities have not identified, had a blood-alcohol level above the legal limit of .10 percent. The man has not been arrested.

"It is clear that the operator's inability to function was the critical element," Glynn said. "There is no better argument for random drug testing than what we've seen in the last few days."

The driver initially claimed the brakes had failed, but tests showed there were no equipment problems, officials said.

Although trolleys are supposed to slow to 6 mph as they approach the subway platform, the train that crashed into another was traveling at least 20 mph, Glynn said. Its exact speed at the time of impact had not been determined.

Glynn ordered random drug testing of MBTA drivers, door guards and police to begin in a month, despite longtime union opposition. The order would affect about 2,350 of the transit system's 5,000 employees.

Officials with the Carmen's Union, which represents the transportation workers, did not immediately return a telephone call seeking comment.

During the first half of this year, the MBTA fired 36 workers for drug or alcohol abuse discovered either because of absenteeism or because it was suspected by supervisors.

The two dispatchers who received complaints about the driver from passenger Tony Niederberger were reassigned to other jobs, Glynn said.

Niederberger said his warnings were handled too slowly to prevent the accident. "We had to be going 70 {mph}," said Niederberger, who attended the news conference with MBTA officials. "I honestly thought that we were going to jump the tracks. The man did not seem to be satisfied with how fast he was going."

The 64-year-old driver, a 20-year MBTA veteran, had no previous incidents of alcohol or drug use on his record, officials said.

He also had no lengthy episodes of absenteeism, often a sign of alcohol or drug abuse.