In addition to focusing attention on mechanical concerns about the freight trains that haul crude oil to refineries, the Lac-Mégantic, Quebec, train crash is reviving debate about allowing rural cargo railroads to operate trains with just one professional on board.

All told, only a handful of trains in the United States and Canada operate with just a locomotive engineer — and no conductor — on board. But Edward Burkhardt, the CEO of the Montreal, Maine and Atlantic Railway Inc. was quoted last week as saying that “one-man crews are safer than two-man crews because there’s less exposure for employee injury and less distraction.”

Safety officials are still investigating the causes of the deadly train derailment in Canada. But critics of one-man operations have wondered if a second employee on the train might have noticed something amiss and taken steps to avoid the accident.

The Federal Railroad Administration published a report last year that stressed that having conductors on trains in addition to the locomotive engineer serves “an important role in handling unanticipated events as well as keeping the locomotive engineer alert, especially on long monotonous trips where there is a risk of falling asleep.”

Despite that, the agency denied a request by the United Transportation Union and other labor groups in late 2009 to ban single-operator trains. There remains no requirement for second operators on freight trains.