I did find a GAO study that said that trains increased in length by 25% since 2008.
But the number of derailments dropped by more than 25% during that time, so the probability of a given car being involved in a derailed train still decreased.
There's been other coverage of the ironically named "precision scheduling" in the rail industry causing a lot of labor problems, because it makes for nightmarishly unpredictable schedules for workers. They never know when a train is going to leave until it is full, so after working a shift, workers stay in a hotel waiting for a return trip that they won't know about until 90-120 minutes ahead of departure. I am guessing that the claims around increased derailment may actually be about frustration with the work environment.
But the number of derailments dropped by more than 25% during that time, so the probability of a given car being involved in a derailed train still decreased.
There's been other coverage of the ironically named "precision scheduling" in the rail industry causing a lot of labor problems, because it makes for nightmarishly unpredictable schedules for workers. They never know when a train is going to leave until it is full, so after working a shift, workers stay in a hotel waiting for a return trip that they won't know about until 90-120 minutes ahead of departure. I am guessing that the claims around increased derailment may actually be about frustration with the work environment.