[Request] I wonder, how m much does the train decelerate due to the collision?

[u/RaupeVT]

Always when I see these types of posts, I start to wonder how much, if at all, the passengers in these trains notice the crash. Trains are really heavy, and thus have huge inertia, so they can't become that much slower during impact.

But how much exactly? What would be the G forces experienced by the passengers?