TOWSON, MD., FEB. 16 -- Former Conrail engineer Ricky L. Gates pleaded guilty today to one count of manslaughter in the deaths of 16 Amtrak passengers killed last year near Baltimore in the bloodiest wreck in Amtrak history.

Gates, who acknowledged in a statement today that he had smoked marijuana in the train minutes before the accident, pleaded guilty to a single count of manslaughter by locomotive in the fiery crash, as part of a plea arrangement in which 15 other manslaughter counts were dropped. Some relatives of the victims appeared distraught and said they were angered by the plea agreement. Many wept during the 90-minute proceeding.

Gates was at the controls of a string of three Conrail diesel engines on Jan. 4, 1987, when they ran through a switch and rolled into the path of a high-speed Washington-to-Boston Amtrak train carrying more than 600 passengers. In the crash and explosion that followed, 16 passengers were killed and 176 injured.

In a statement supporting the guilty plea, Gates acknowledged publicly for the first time that he and Conrail brakeman Edward Cromwell smoked portions of a marijuana cigarette minutes before the crash occurred. After both took about three drags from the cigarette, Cromwell then took the remaining marijuana and smoked it in a pipe, the statement said. After the crash, Cromwell returned to the train, found the pipe and threw it away in a yard adjacent to the tracks, the statement said.

Experts earlier had reported finding traces of the illicit drug in the blood and urine of both men, but said they could not pinpoint when it was ingested or determine whether it impaired the two men.

The statement also said both men lied to investigators about events leading up to the crash and had ignored a list of safety equipment tests on the locomotives before the crash occurred.

Additionally, Gates was described in the statement as upset at media reports on the crash while talking with friends at a bar three days after the accident.

He said he felt "the media was not telling the truth," according to the statement, and said he was "going to try to sell his story for a million dollars."

The single count to which Gates pleaded today was amended to include the names of all 16 victims, but he faces a possible maximum penalty for only one count -- five years in prison and a $1,000 fine.

Under a five-year sentence, Gates would become eligible for parole consideration after about 20 months in prison.

Prosecutors asked that the full five-year sentence be imposed.

Baltimore County Circuit Judge Joseph F. Murphy scheduled sentencing for March 29. Gates remains free on bond until then.

While the guilty plea closes the criminal aspect of the case, the agreement with prosecutors appeared to stir some discontent among several members of victims' families and their attorneys.

Several said after the proceeding that the five-year maximum penalty would not adequately reflect the gravity of Gates' acts.

"Facing a maximum of five years in the face of all this carnage is hardly proportionate," said Roger A. Horn of suburban Baltimore, father of 16-year-old Ceres Horn, one of the 16 victims. Under Maryland law, "it's not as serious as stealing a refrigerator or a television set."

John P. Coale, an attorney for several passengers and family members in civil litigation against Conrail and Amtrak, said he found prosecutors' willingness to accept a single manslaughter plea "a bizarre action." If Gates is sentenced to a five-year term, Coale said, "that comes to about 3 1/2 months per person" killed.

He described the amendment of the manslaughter count to include all 16 victims as a "p.r. move."

Sandra A. O'Connor, Baltimore County state's attorney and chief prosecutor, said the plea agreement was reached, among other reasons, to avoid an emotionally wrenching trial and to "make the proceedings easier on the victims."

Also, O'Connor said, the plea forces Gates to acknowledge his guilt publicly, and brings "certainty and finality to the proceeding."

She said, "It is hoped that addressing {Gates'} conduct as a crime will send a message to others who themselves as operators of common carriers are daily responsible for human life."

Horn, a mathematical sciences professor at Johns Hopkins University, said the public should look beyond the Gates case and lobby for national legislation tightening rules and drug monitoring for train crew members.

Gates' plea came after lengthy negotiations with prosecutors and an indictment that relied heavily on the testimony of Cromwell.

Cromwell, who had been granted immunity in the investigation, also was expected to be a key prosecution witness if Gates had gone to trial.

The statement, read in court today by Assistant State's Attorney John P. Cox, recounted how Gates and Cromwell were called to a Baltimore area freight yard to take the three locomotives to another yard near Harrisburg, Pa.

While checking the locomotives, the men failed to replace a missing light bulb on a cab signal capable of warning them not to enter the track on which the Amtrak train was traveling, according to the statement.

They also failed to remove a piece of tape that blocked the sound of an emergency whistle also designed to warn them not to enter tracks carrying other trains.

Once out on the track, according to the statement, Cromwell produced a hand-rolled marijuana cigarette.

"Each man had about three hits of the joint," the statement said. "Then Cromwell smoked the remainder in a pipe."

By then the three Conrail locomotives were moving at about 60 miles per hour, according to the statement.

They passed at least two trackside signals warning them to slow down and stop to allow the northbound Amtrak passenger train to pass them before entering the Amtrak track, the statement said.

Moments before the collision, Gates slammed on the emergency brake, the statement said. The locomotives jumped the switch and seconds later, the Amtrak train slammed into the rear of the locomotives at 105 miles an hour, the statement said.