Federal safety officials blame the fatal head-on collision of two Conrail freight trains last year on work schedules that deny train crews normal sleep.

The National Transportation Safety Board, in a ruling Tuesday, asked the railroad industry to "make an in-depth assessment" of what it can do to ensure that crews operate trains without falling asleep at the controls.The railroad industry has long had unpredictable work schedules, but the problem has worsened, the board said. It blamed the elimination of many regularly scheduled freight and passenger trains, a cutback in yard operations, agreements protecting employee seniority, longer freight runs and relocations of work assignments.

"Under present conditions, many train crew members may well work their entire careers without ever having a job with regularly assigned working hours and off-duty periods," the board said, adding that this leads to sleep disorders.

The recommendations came in a report on a Jan. 14, 1988, crash that killed four men - two engineers and two brakemen operating Conrail trains that plowed into each other outside Thompsontown, Pa.

The board concluded that engineer Melvin Russell Curry, 40, and brakeman Francis Joseph Madonna, 46, were asleep when warning devices went off and said Curry likely responded to the warning by hitting a foot pedal in his sleep, deactivating an automatic braking system.

Killed in the crash in addition to Curry and Madonnna, were engineer Russell Paul Henderson, 30, and brakeman Charles Stephen DeSantis, 56, who were operating a 61-car train headed from Chicago to Harrisburg, Pa.

The two trains were moving at a combined speed of 71 miles per hour when they collided, with one locomotive plowing over the top of the other one.