Based on the video evidence I saw yesterday there was a hot box on one of the cars - likely caused by a stuck hand brake OR overheated or failed bearings on an axle. This generated a massive amount of heat and eventually metal fails when heated beyond its capacity. You fail an axle at speed on a heavily loaded train and you are going to get a derailment.
The engineer either ignored or failed to recognize the problem (I doubt this - they have sensors along the rail lines that should have notified him that he had a “hot box”) or the engineer was denied permission to stop the train and address the problem because blocking a rail line can costs millions of dollars per 30 minute increments. The video below shows what was happening 20km prior to the derailment. They should have stopped the train.
https://www.youtube.com/watch?v=DHiXZUgQEwc
A “hot box” is the term used when an axle bearing overheats on a piece of railway rolling stock
Air brakes work for trains but the bigger the train the harder it is to stop and there are shortcomings for air brakes in these situations.
The obvious changes that I expect are to limit the size of trains carrying hazmat materials AND to implement a mandatory stoppage and fire department response to a hot box.
Profit has to be balanced against risks. Boeing just learned a hard lesson about this and I suspect that the railroads are on the same path at the moment.
I'm surprised there isn't already rule in place!.............
Harder?
Even when each rail car has it's OWN brakes?
I can understand a braking difference for an unloaded vs loaded semi truck.