A corridor coach is a type of railway passenger coach divided into compartments and having a corridor down one side of the coach to allow free movement along the train and between compartments.
These were first introduced, in Britain at least, around the start of the 20th century, because the advent of dining cars made it advantageous to enable passengers to move down the length of a train. This was achieved by linking the corridors of adjacent coaches using a "corridor connector".
Corridor coaches still persist in former Eastern Bloc countries for several reasons over Western European "open" types including increased warmth in winter by having a cabin door keeping gangway draughts out. Trains coaches moving at high speed can become cold from frequent gangway access. The heating systems are low drawing electric systems from diesel electric engines outside the American Northeast Corridor. For example the Amtrak Silver Meteor train from New York to Florida ,frequently used in winter to escape the cold north, it chilly from poor heating and draft from gangway traffic. Secondly , Eastern European countries sell standing room only tickets on rural routes where people stand in the corridor if the cabins are full of that was the purchased ticket, still seen in Poland. This is not possible with an "open" arrangement as the standing passengers would not be separated by a door as in the corridor coaches.
The corridor coach was known on the European continent as the American system or American coach in the early 1900s.