I could imagine this as a large modern day train. A plane usually holds about 60 or so people. Being that this is a train I could imagine it to be closer 100 or 150 people for the capacity. As far as size goes it's up to you. If it's a train I suggest looking into some real train cars for a better idea. Here's some example sizes: 20m long, 3m wide, and 4m high. A room could be about 2m long, 1.5m Wide and as tall as the car. This means there's 1.5 Meters for walking inside the car along the length of the car which could be a 1.5m walkway or two .75m walkways on both sides. This means about 9 rooms per car with about a 1 meter on both ends of the car for the in between areas. If each room is designed for about 4 people per room that's 36 people per car not including anyone or anything servicing the guests. So if you had a small train with 1 Car devoted to storage, 3 Cars for people and 1 engine: Total Length of train: 100M Total amount of passengers: 108 Now the average time is about 7-9 hours of a trip, based on the fact it's close to a transatlantic flight, so don't forget that too!