Basically, the game is about connection destination cities on a mapboards with plastic train pieces of the color assigned to a particular player. Each route is marked on the board in a certain color. There are train cards available each turn to match the colors on the board.
So in effect it is a card set collection game much in the way that Rummy is. On each turn there is a stack of facedown train cards and five which are face up next to the deck. A player can choose two cards that can either be face down or up. There are locomotive cards that are wild but if they are selected face up, that is the only card a player can choose that turn.
Bonuses are given for completing Longer routes are depicted on map cards that are also available to each player. A shorter route between two cities is worth victory points dependent on the number of trains needed to complete. The route cards make it mandatory to connect mutiple cities and those points are worth more points.
Once a player is down to three train pieces, the game has just one more turn and it is over, with the person winning who has the most points.
The original game has a map of the U.S. There is also a version with Europe and then several map boards to play in other geographic areas.
“Alan R. Moon has always insisted that it's not just new maps that matter, it's small changes to the game play that make each of the follow-on editions so interesting and fun to play,” said Kaufmann. “The core game play always remains the same, but small changes can make a big difference in how to map out the best strategies.”
for instance, Europe introduced station pieces to handle a more crowded gameboard.