The National Transportation Safety Board yesterday found that a severely worn steering assembly was the probable cause of a commuter bus crash on I-95 near Quantico in February that killed 11 and injured 13.

Board spokesman Robert Buckhorn said investigators concluded that a worn ball-joint connection caused the steering linkage to jam, leaving the driver unable to control the bus, which was traveling 50-60 mph.

The NTSB also found that two other factors contributed to the accident:

"Ineffective inspection procedures followed" by D&J Transportation Co. of Fredericksburg, owner of the bus, and by the Virginia state inspection officials "caused the failure to detect" the worn parts of the steering mechanism.

Also at fault, the board said, was the design of the steering system that "included mechanical components that could gradually deteriorate with no forewarning of impending failure and did not incorporate failsafe features."

The NTSB went on to recommend that the U.S. Secretary of Transportation evaluate state regulation of commuter bus driver qualifications, inspection of vehicles and vehicle maintenance records.

Also recommended was state regulation of commuter bus use and an agency in the transportation department to provide technical guidance to owners, operators and inspectors of commuter buses. The agency also would record accident data and safety statistics on commuter buses.

The report also concluded that:

The bus driver, who was killed in the accident, was not incapacitated at the time and that the accident was not attributable to driving performance. Though witnesses suggested the driver did not apply his brakes, the board found light tire marks, though the marks were too "faded to make a determination on the question of whether brakes were applied," spokesman Buckhorn said.

The guardrail over which the bus plunged 25 feet into a creek was "not designed to contain or redirect large vehicles," Buckhorn said. "Its height had been reduced by the buildup of soil over the years since it had been put in place." Buckhorn said the board recommended the state start a program to remove dirt and debris around guardrails.