Mexican Train

Mexican Train is a game played with dominoes. The object of the game is for a player to play all the tiles from their hand onto one or more chains, or trains, emanating from a central hub or "station". The game's most popular name comes from a special optional train that belongs to all players. However, the game can be played without the Mexican train; such variants are generally called "private trains" or "domino trains". It is related to the game Chicken Foot.

Equipment

A double-twelve set of dominoes is marketed as the standard for Mexican Train, and accommodates up to eight players, but there are many sets that are commonly used. The following sets can be used, depending on the number of people playing:

Double-six
Double-nine
Double-twelve
Double-fifteen
Double-eighteen

Many domino sets use color-coded pips or numerals for the values to help players select matching domino values; however, the color coding scheme may vary from set to set.
In addition to dominoes, the game also uses:

One token or marker for each player
Pencil and paper to keep score
A special spacer, known as the "station" or "hub", used to evenly space the trains around the central domino in radiating spokes

Many sets of dominoes include a station and special train-shaped tokens for markers, and packaged games with a central "station" and custom tokens are available, along with pads to help keep score. However, the station piece is not strictly needed, and anything from coins to poker chips to even pieces of candy or slips of paper can be used as markers. Because the station or hub usually is designed for eight spokes, the maximum number of players is eight, although additional spokes may be laid in between slots to accommodate more players, using larger domino sets.

Objective

The objective of all train games is to be the first to place all your dominoes. Dominoes may be placed onto the player's train, onto the Mexican train if available, or on the trains of other players under special circumstances. The middle tile counts as the start of a player's multiple tile train.

Gameplay

There are many different rules for Mexican Train, typically with slight variations in gameplay and adjustments according to personal or family custom; the version presented in this article is an amalgamation of rules from Parsons, Galt, and Bauguess, using additional rules as needed to check for consensus as there is no single, definitive rule set. Exceptions and variations are noted.

Setup and start

At the start of each round, the dominoes are placed face-side down, shuffled, and each player draws an equal number to form their hands. The actual number drawn depends on the number of players, domino set in use, and rule variation in use. For example, for a 3-player game using the double-twelve set of 91 dominoes, each player draws 15 tiles for their hand, under the 1994 Galt rules. Dominoes held in a player's hand are kept hidden from the other players.
Any remaining dominoes are placed to one side, forming the "boneyard". For example, under the 1994 Galt rules, in a 3-player game using the double-twelve set of 91 dominoes, the players collectively hold 45 tiles, leaving 46 tiles in the "boneyard".

Opening the station

The highest double tile is set aside before shuffling the tiles and placed to "open the station", starting the game; e.g., with a standard double-twelve set the double twelve is separated before shuffling and placed in the center of the station hub. In each successive round the next lower double is used until all doubles are used. The double-blank is used for the final round; however, players may agree to play fewer rounds in a complete game, especially when sets larger than double-nine are used.
Alternatively, in the 1994 rules written by David Galt, the player who is designated to take the first turn places their highest double in the station to start the game. If the first player does not have a double, the next player opens the station with a double. If no players have a double, each player takes a turn drawing one tile from the boneyard until a double is drawn and used to "open the station".
The player designated to go first should change with each hand. Galt suggests the first player role should rotate so that each player has an equal number of chances to go first. Other rule variants suggest alternative methods to select the first player:

The first player is selected at random, then rotated clockwise.
The first player for the first round can be selected by age, then rotate clockwise for each following round.
Each player draws one tile from the boneyard after shuffling. The player who selected the highest total pip count is designated the first player for that round. The drawn tiles are shuffled back into the pile before drawing hands.
The first player is the one who holds the double-12 domino after drawing hands.
Basic rules

A legal play is made by matching pip values, i.e., the domino being placed is oriented so the pip value on one end of that domino matches the pip value on the free end of a domino which is already on the table.
A player may choose to play their domino on their private train, any marked public train, or the Mexican Train, which is a common train which remains public throughout the game.
There is no option to pass a turn. When the player holds one or more dominoes that can be played legally, at least one domino must be played from their hand.
When the player holds no dominoes which can be played, that player must draw one domino from the boneyard and play it if the drawn domino can be played. If the drawn domino cannot be played, or if the boneyard is empty, that player must designate their private train or the side of the station facing them, if no private train has been started, as public, by placing a marker.
After a double domino, i.e., a domino with identical values on both ends, is played legally, that double must be covered by the player who placed it, meaning that player must immediately play another domino legally next to the double. Responsibility to cover the double passes to each player in turn until the double is covered.
Opening phase

The first player then starts a private train, sometimes known as a personal train, by placing a tile that legally starts from the station by matching pip values to the engine in the station hub, in a direction leading towards their seat. Each player takes a turn, mirroring the first player's first move by playing one tile starting from the station hub in a direction that leads toward their seat.
In other rule variations, during the opening phase, players may start and build their private trains by using as many dominoes as possible from their hand, radiating out from the station hub towards their seats, instead of placing a single domino. Once each player has built these private trains as long as possible, players then start to take turns, placing one or two tiles per turn using their remaining tiles, until one player has emptied their hand, ending the round.
In the 1994 Parsons rules, each player separates their hand into two categories: "personal train" and "extras", with the "personal train" being the longest possible string of end-matching dominoes starting with one that can be laid into the central station hub, and the "extras" being the leftover dominoes that do not fit into the "personal train". With their first move, the first player may choose to start either their "personal train" or the "Mexican Train", using one of the "extras" that has an end matching the "engine" in the station hub.

Train building

After the initial opening phase, players take turns placing one or two of their remaining tiles legally on any eligible train, which is either their private train, any public train, or the always-public Mexican Train. Two dominoes may be played only when the first domino played is a double. Play continues from the first player to the left. A player may not pass their turn, as the boneyard-draw rule or double covering rule may require that player to designate their train as public.
A train can be as long as the players can make it; it ends only when all dominoes that could match its endpoint have already been played. As a result, trains can become quite long, especially with an extended domino set. It is acceptable to "bend" the train 90° or 180° to keep the train on the playing surface, as long as it does not interfere with the endpoints of other trains.

Public and private status

During their turn, a player may choose to play a domino on any train currently marked public, regardless of whether it is possible to play on their own private train.
When a player is unable to place a domino before their turn ends, they must mark their private train as public by placing a marker on their train. After a player legally plays a domino on their marked public train, i.e., the train with their marker, it reverts to being private and may not be played on except by the train's owner, unless it is forced to become public again. To designate when a train is private, the marker may either be removed altogether or moved to the station hub, depending on the rules.
The marker on a public train can only be removed by the marker's owner to make it private, and there is one marker per player. In other words, a player may not hold more than one private train at a time. Only the player whose marker is on a public train can turn the train private by making a valid play on that train and lifting the marker. For example, if Player B places a domino on a public train with Player A's marker, that does not force that train to become private for Player B; when Player A's turn comes, after Player A makes a valid play on that public train, only then will it become private.
If a player is deemed to have made a strategic error the highest score of that round is added to theirs.