Rescue workers dig through the rubble of an Amtrak passenger train that collided with three Conrail locomotives in Essex, Md., in January 1987. (Fred Kraft/Associated Press)

Federal regulators, faced with soaring drug use among railroad workers, have rejected an industry request to postpone required testing for the more than 36,000 employees who maintain rail lines.

“The country is in the throes of a devastating substance abuse ­crisis,” said Sarah E. Feinberg, who heads the Federal Railroad ­Administration (FRA). “The rail industry and its workforce are not immune from this crisis — we know that in fact many are ­suffering.”

Feinberg on Thursday rejected a petition to extend by one year a drug and alcohol testing requirement set to take effect in June.

“Delaying track workers from being included in the group of railroad employees tested for drugs and alcohol would delay the important work of preventing ­injuries and fatalities,” Feinberg said.

The Association of American Railroads (AAR), which represents freight railroads, signed the petition, but later withdrew its objection.

“Freight railroads in the country already have drug and alcohol testing programs in place for employees, support the rule and can meet the 2017 deadline for track workers, this is a priority for the industry,” AAR spokesman Ed Greenberg said.

Nearly 8 percent of workers ­involved in rail accidents this year tested positive for drug use, ­including marijuana, cocaine, ­ecstasy, benzodiazepine, OxyContin and morphine, according to internal federal documents ­obtained by The Washington Post in September.

That number was the highest since the FRA began keeping ­records in 1987 and three times higher than it was 10 years ago.

Overall, the number of engineers, train crew and dispatchers who tested positive for drug use in random tests rose by 43 percent last year. After rail accidents in 2014, no one tested positive for drugs, and just two people did last year.

Railroad drug-testing has been limited to about 120,000 “safety sensitive” workers whose performance puts lives at risk. The train-repair workers and about 70 percent of the more than 36,000 workers who maintain track beds and railroad right-of-ways are not yet required to undergo the same testing.

The U.S. Transportation Department drug-tests about 7 million people who hold commercial driver’s licenses, as well as railroad and transit workers, and the U.S. Coast Guard. In the past five years, the DOT tests have shown sharp increases in use of amphetamines and natural opiates.

The popularity of illegal prescription drugs and heroin has increased dramatically in the United States. in recent years. A record 28,647 people died of heroin and prescription opioid use in 2014, according to the Centers for Disease Control and Prevention. Overall, 47,055 people died of drug overdoses in 2014, the CDC said.

The FRA and the railroads it regulates have been at the forefront of federal drug testing since 1987, when an Amtrak train collided with three Conrail freight locomotives linked together just north of Baltimore.

The engineer and 15 others on the Amtrak train were killed; 174 other people on the trains were injured.

Investigators determined that the engineer of the Conrail train and his brakeman had shared a marijuana joint as they made their way from the rail yard. The engineer, Ricky Lynn Gates, was convicted on state and federal charges and served four years in prison. In 1993, he told the Baltimore Sun that smoking marijuana was the cause of the crash and that it was not the first time he had done it on the job.