The National Transportation Safety Board (NTSB) found yesterday that flaws in personnel screening and safety equipment were behind two light rail accidents last year at Baltimore-Washington International Airport, and the board called for nationwide changes in how transit agencies monitor their employees' medical and drug-related problems. The safety board blamed both crashes on operator error, but said both could have been prevented or might have caused fewer injuries had the Maryland Transit Administration been more vigilant. The first accident, in which 18 people were injured Feb. 13, was caused by an operator impaired by cocaine, prescription drugs or both, according to findings released yesterday by the safety board. The light rail train slammed into a steel barrier at the end of the track. The second crash, which hurt 17 people Aug. 15 when a train ran into a different barrier at the same spot, resulted from the operator's undiagnosed sleep disorder, which caused him to nod off at the controls, the board concluded. In each accident, the board noted that the operator's failure to apply the brakes resulted in the train hitting the bumping post and that, prior to the two accidents, the MTA had not successfully implemented a comprehensive system safety program plan throughout all levels of the organization. Efforts to do so are currently underway. The board recommended the following to all transit rail systems:

• Require employees in safety-sensitive positions to inform the system about the employees' use of prescription and over-the-counter medicines so that the rail system can have qualified medical personnel determine the medicine's potential effects on employee performance, and train employees about their responsibilities under policy.

• Ensure fatigue educational awareness programs include the risks posed by sleeping disorders, the indicators and symptoms of such disorders and the available means of detecting and treating them.

• Install, on all light rail vehicles, independent event recorders that record and retain the most recent 48 hours of data, store data in a nonvolatile memory and have a back-up power source that would enable the entire recording system to function if electric power is lost to the car.