I talked to a retired engineer this week, who explained to me about the new schedules and how many engineers were operating on only six hours' sleep:

Investigators trying to determine the cause of Tuesday's deadly Amtrak crash have still yet to speak in depth with Brandon Bostian, the engineer who was piloting the train as it sped up to 106 miles per hour around a sharp curve. But the union representing those engineers say that recently-implemented schedule changes might have left him in a fatigued state that could have lessened his concentration.

On March 23, engineers on the Northeast corridor got new schedules that left them either with very short turnarounds between runs, or with very long breaks that extended the periods of time they spent away from home, according to the Brotherhood of Locomotive Engineers and Trainmen. The changes, which the union says Amtrak told them were necessary to achieve cost savings, also created more variability and unpredictability. That can be hard on an engineer's internal clock.

"We feel 100 percent confident that the issue of the new schedule, the reduced rest period and layover period for this young man, was an immediate and direct contribution to this incident," Fritz Edler, chair of the local committee of adjustment for the BLET's Division 482, said in an interview Friday. "Fatigue is a cumulative problem. So if you have a bad day yesterday, it’s going to be that much harder to do your job today. And that’s the kind of situation [Bostian] was up against."

Amtrak did not immediately respond to a request for comment.

The trainmens' union has been warning for months that the proposed changes could have adverse impacts. In September, they sent a letter to Amtrak's superintendent of operations warning that attempts to save money through asking engineers to work more shifts with shorter breaks could put them in danger. In November, Congresswoman Eleanor Holmes Norton (D-D.C.) followed up with a letter urging Amtrak not to go forward with the new schedules.

In December, the union sent another letter (first reported by NBC News) that expressed frustration that Amtrak was moving forward with the changes, despite what it called "false assumptions" in the computer models that had put together the new shifts.

"We understand that there are legitimate and sound business savings to be had at Amtrak," Edler wrote in the December letter. "But forcing known sources of fatigue on the trainmen and engineers for experimentation is not one of them. We are confident that the riding public and communities we work in and serve would reject such moves if they knew about it."

In February, union representatives met with top Amtrak officials asking for a halt to the changes. Finally, on March 13, the union appealed to the Federal Railroad Administration for an audit. "Our experience is that both these issues are now demonstrated to be a change in Safety Culture that can no longer be addressed internally," the letter reads. "We believe these policies have and will result in unnecessary increased risk, especially regarding fatigue mitigation."

Nevertheless, the new schedules are now in effect.

"Every engineer working between Washington and New York, basically, are either in a situation where they’re working with shorter turns or with longer periods away from home," Edler said in the interview. "What nobody is doing is saying, why don’t we go to the people who actually do the job every day and ask them what they need to do the job safely?"

By the way, this kind of scheduling was a major issue in Bay Area Rapid Transit negotiations last year.