In a move that might have spared those involved in a deadly Amtrak derailment in Philadelphia last year, federal regulators Monday said they want a minimum of two engineers aboard most of the nation’s trains.

The proposal has been under discussion since before the May 13, 2015, Amtrak derailment that killed eight people and injured more than 200 when a train traveling twice the posted speed limit spun off the tracks on a curve. Engineer Brandon Bostian was alone at the controls. He said afterward that he had no recollection of why the train gathered speed, remembering only that he slammed on the emergency brake as it rounded the curve. Had he shared the locomotive with a second engineer, the sudden increase in speed might have been noticed.

The Federal Railroad Administration now has proposed requiring two engineers on most trains, making an exception for those trains that pose little safety risk.

Association of American Railroads President Edward R. Hamberger responded that “There is simply no safety case to be made for a regulation that requires two-person crews, especially where positive train control is fully operational.”

Positive train control is an emergency braking system that automatically kicks in when a train exceeds safe speeds. Federal officials have said that had it been in use, it would have prevented the Philadelphia derailment.

“Notwithstanding an extensive body of evidence showing that two-person crews are no safer than one-person crews, the nation’s Class 1 freight railroads currently operate with two-person crews, and have committed to continuing that practice for trains without PTC systems in place,” Hamberger said.

Class 1 freight railroads account for almost 70 percent of overall miles logged on the rails each year. The seven Class I railroad companies are BNSF Railway, CN, Canadian Pacific, CSX Transportation, Kansas City Southern, Norfolk Southern, and Union Pacific.

“Even the FRA concedes they have no ‘reliable or conclusive statistical data’ to suggest that two-person crews are safer,” Hamberger said. “I encourage the FRA to reexamine the facts and exercise sound regulatory judgment before finalizing a rule that lacks empirical support.”