Impaired operators -- one using drugs and the other groggy from a sleep disorder -- caused two nearly identical light-rail crashes at the Baltimore-Washington International Airport station last year, according to findings released yesterday by the National Transportation Safety Board.

The Feb. 13 and Aug. 15, 2000, accidents, in which 35 people were injured, were made worse because the airport station had the wrong type of bumping posts, the safety board found. And the posts were improperly installed, investigators said.

The safety board has recommended that Maryland and other transit systems require operators to disclose the kinds of prescription and over-the-counter drugs they are using and to recognize whether they suffer from a sleep disorder that could interfere with the operation of vehicles.

Before the accidents, the Maryland Transit Administration did not require employees who operate trains, buses or light-rail vehicles to disclose whether they were taking a prescription drug.

MTA spokeswoman Suzanne Bond said that will change next month, when the agency will begin retraining all 2,450 workers in "safety sensitive" jobs and instruct them to report the use of prescription or over-the-counter drugs and whether they have sleep disorders that can interfere with their jobs.

"We want them to realize that if they have a fatigue problem, they have to deal with it," Bond said.

The drivers in both crashes were using over-the-counter painkillers at the time of the accidents. The operator in the February accident, Sam Epps Jr., also tested positive for cocaine use. He was fired.

The driver in the August crash, Dentis David Thomas, had an undiagnosed case of sleep apnea and fell asleep moments before the crash. He was also fired but has been reinstated and now works as a station attendant in the Baltimore subway, Bond said.

Since the accidents, the MTA has invested $30 million in safety devices, including a braking system that kicks in automatically if a train is going too fast as it approaches the airport station, Bond said.

The agency now also requires light-rail operators to stop at a red signal and manually select a track before entering the two-track station. The speed limit in the station has been cut from 15 mph to 5 mph, Bond said.

The MTA has also installed stronger bumping posts at the station, after the safety board found that the kind in use during the accidents was not strong enough.

Bond could not say why the MTA installed the wrong type of bumping posts.

"We've been working with the NTSB throughout the investigation," she said. "We installed stronger posts and concrete. . . . The bottom line is, we have for the safety of our passengers the stronger bumping posts and type of equipment."

The safety board also recommended that the MTA install event recorders on its 53 light-rail cars that would help investigators better reconstruct events that lead to a crash. Bond said her agency would buy the recorders and install them within a year.

To avoid crashes such as this in February 2000, the National Transportation Safety Board recommends requiring operators to disclose medications.