Reserved seats are marked by a paper stating which seat and for which route is reserved. These are normally on the side of the windows. If a whole carriage is reserved, there is a paper stating again the route on the door to the train. Some times you will see a paper stating express reservation.
Non reservable trainSome carriers don't provide seat reservations on all or some of their trains. This is common on regional trains, shorter routes and during peak travel times on commuter routes. On these trains you can sit in any vacant seat in the class your ticket is booked for.
The train operator may not have released seat reservations at that time. The train operator will only open seat reservations when the train path has been confirmed by Network Rail. This is usually 12 weeks ahead of your travel date. The train on which you wish to travel is full at the time of booking.
Your seat will be automatically assigned when you complete your reservation. You may change your assigned seat at any time after your booking is complete using interactive seat maps on the Amtrak app or on Amtrak.com. There is no fee to change your seat.
Seat reservations aren't guaranteed though and some Train Operating Companies (TOCs) don't offer seat reservations at all. Even without a seat reservation your tickets are still valid, and you can sit in any vacant unreserved seat. Sit in any vacant unreserved seat except First Class.
Some routes are simple, open seating.However, others, such as long-haul trains, have assigned seating. However, you'll usually find there are plenty of open seats you can switch to; just make certain with the conductor that the seat isn't reserved for passengers boarding at a stop further ahead.
It's pretty logical that the front car is the most dangerous place in a head-on collision, and the last car worst if the train is rear-ended, so National Association of Railroad Passengers president Ross Capon suggests riding in the middle cars.
Starting from September 30, 2023 Trenitalia will slowly introduce a mandatory CHECK IN policy for Regional Train ticket holders. As a result, any regional train tickets specifying NOT VALID TO TRAVEL will require a CHECK IN to be performed which would be a process to validate the tickets for usage.
If you are caught with a reserved ticket for another train, you will be treated the same way as travelling without a ticket. A hefty fine will be imposed and the railways may also take legal action. If you miss your train with a reserved ticket, you have no option but to reserve a seat again for the next train.