AI trains accelerate and decelerate much too fast in the game. Currently, I would rank this among the most unrealistic aspects of gameplay. I would say that as a rule of thumb, halving the acceleration and deceleration rates would probably give results that are a bit closer to reality. In some cases, even further reductions might be necessary.
In some past discussions on TS 2019 forums, it is my understanding in that sum, AI does not follow the physics the player consists does. This was supposedly for performance reasons.
I understand that, but that just means the acceleration/deceleration rate is set to some fixed value, rather computed on-the-fly. Nothing should prevent the devs from adjusting this rate to a more realistic number.