WASHINGTON (AP) _ The engineer of an Atchison, Topeka and Santa Fe freight train was asleep when it collided with another train in Corona, Calif. last year, killing four people, federal safety officials said Tuesday.

The National Transportation Safety Board said that the brakeman and conductor failed to prevent the early morning accident, ''probably because they were asleep'' also.

The safety board blamed ''chronic and acute'' fatigue in the crash which killed the engineer, brakeman and conductor on board train 818, westbound from Barstow, Calif. The accident also killed the brakeman and seriously injured the engineer on train 891, eastbound from Hobart Yard in City of Commerce, Calif to Chicago.

The board said the engineer had last been in bed 26 hours and 41 minutes prior to the collision. He arose initially expecting a shift that did not materialize, then drew a later one, it said.

It said a witness, a night watchman in a nearby warehouse, described the engineer as not moving and showing no visible signs of wakefulness seconds before the 4:11 a.m. crash.

The engineer's fatigue was a result of the ''irregularity and unpredictability of his work schedule,'' the safety board concluded.

And it said the railroad had never addressed the issue of an employee notifying management ''concerning his or her lack of sufficient sleep.''

Therefore, the board said, the railroad's lack of a policy to remove crews from service when they are not properly rested contributed to the accident.

It recommended that the American Association of Railroads and railroad unions develop a policy to allow a railroad to prevent an employee from accepting assignments ''when the employee is impaired by lack of sleep.''

The board said the accident occurred when train 818, pulled out of the Corona siding, passed a stop signal, and entered the main track. The eastbound train 891 collided with it, head on.

The board said that when the engineer of train 891 saw the signal light at Corona suddenly turn red, ''it was too late to take action to avert the accident.''

And it said that while traces of unspecified drugs were found in the urine of the engineer of train 891, ''his actions did not contribute to the accident.''