There are three transport prisons in the game:
Transport Prisons take place on vehicles - Cougar Creek Railroad is a train, HMS Orca is a ship and Air Force Con is an airplane. As such, gameplay features are affected by the fact that you are on a mobile vehicle, traveling toward a destination. (See #Gameplay for gameplay differences.)
The layout of the prison is different, but has some similarities to ordinary prisons. There exists a cell block (where you spawn, as normal), an infirmary (players are not sent here, only knocked-out Guards - players will be sent back to their cells), and what appears to be a meal hall, as well as a Control Room with a contraband desk in it (no locked doors), allowing you to access your items if you lost any on getting knocked out. There is also always a "command center" of the vehicle (it's the locomotive in Cougar Creek, ship's bridge in Orca and cockpit in Air Force con) where several guards reside. These guards are the transport equivalent of Riot Guards, with Metal Batons and ordinary Guard Outfits. Beating up all these guards in Multiplayer allows you to perform an escape.
Transport Prisons have several notable features that differentiate their playstyle from ordinary prisons.
There are no routines on transport prisons. Instead, the game lasts only one ingame day, after which players will fail if they did not manage to escape.
In transport prisons, you are only allowed to be in your cell. Players are the only inmates. If you are spotted outside your cell by a guard, your heat will immediately rise to 100 and you will come under attack. If you lose a fight with a guard, the medics will rush you back to your cell. Medics will not snitch to the guards as to where you are. This gives transport prisons a level of action, as combat against guards is nearly unavoidable.
Items contained in desks on transport prisons are preset - the combined contents of all the desks are the same through every playthrough of any given transport. The items' locations may change - they might show up in different desks across different games - but in one transport prison, the total loot is always the same. This means that Contraband Desks, where confiscated Contraband goes, are easily accessible - otherwise, you could lose an essential contraband item and never be able to escape.
Finally, the last unique part of transport prisons is the escaping. Perimeter Breakouts, present in all non-transport prisons, are nonexistent in transports, as there is no 'perimeter' for you to simply walk over. Instead, each prison has its own unique set of escapes, each sharing one common method: takeover. This is a simple multiplayer-only method that involves beating up the 2 or 3 guards in the 'command center' of the prison (as noted above) and interacting with an object in that area to escape. For more information and tips on all escapes from transport prisons, please see their individual pages.