[XorNot]

Zero.

Trains derail all the time.

From the link below [1]:

From 1990, the first year the BTS began tracking derailments and injuries on a yearly basis, to 2021, there have been 54,539 accidents in which a train derailed. That’s an average of 1,704 derailments per year.

[1] https://thehill.com/homenews/3539221-how-often-do-trains-der...