Mexican Train Conventions: The Engine, Personal Trains, and Doubles

Our comparison guide covers Mexican Train alongside Chicken Foot at a high level; this guide stays with Mexican Train specifically and goes deeper into the conventions that make it feel distinct once you're actually playing — the engine, personal trains, and how a full multi-round match is commonly structured around a shrinking sequence of starting doubles. As with every variant covered on this site, these are widely used conventions for one named game, not a claim about "the" rules of dominoes generally.

The engine: choosing the starting double

Every hand of Mexican Train begins with a double placed at the center of the table — commonly called the engine. Many groups start a full match with the highest double in the set (12-12 in a double-twelve set) and work down from there across successive hands, using 11-11 as the next hand's engine, then 10-10, and so on down through 0-0. That structure gives a full match a natural length: a double-twelve set supports 13 hands this way (12-12 down through 0-0), one for every double in the set, which is a genuinely convenient side effect of the doublesCount(n)=n+1 formula covered on our set reference page — 13 doubles, 13 possible engines, 13 hands in a full match.

Not every group plays a full descending sequence every time; a shorter session might simply play a handful of hands with whichever doubles are drawn or agreed on. But the descending-engine structure is common enough, and clean enough mathematically, that it's worth knowing even if your group doesn't always use the full sequence. A group using a smaller set for Mexican Train — double-nine, say — simply shortens the sequence accordingly: 10 doubles, 10 possible engines, a 10-hand match, following exactly the same n+1 doubles-count logic regardless of which set size is on the table.

Personal trains: build, extend, and mark

Each player's personal train radiates outward from the engine, and the core convention is straightforward: on your turn, you may extend your own train, or add to the shared communal train, or both if you have tiles for it. What trips up new players is the marking rule: if you can't extend your own train on your turn (and have no play for the communal train either), you must draw from the boneyard. If the drawn tile still doesn't let you extend your train, your train is marked "open" — commonly with a small marker, though a spare tile or token works fine — and stays open until you close it yourself with a matching tile on a future turn.

An open train isn't purely a downside: while it's open, any player may play on it, which cuts both ways. Opponents might shorten your options by playing tiles you were hoping to use yourself, but you might also find your open train useful as an extra outlet if your own hand has a tile that fits it and nothing else. Watching which trains are currently open — yours and everyone else's — is one of the more valuable habits an experienced Mexican Train player develops, since it's public information that changes turn to turn.

The communal train

Alongside every player's personal train, one additional train — commonly just called "the Mexican train" — branches off the same engine and stays open to every player at all times, regardless of whose turn it is. It's never marked open or closed the way a personal train is; it's simply always available. Some groups treat starting the communal train as optional (it might never get built on in a given hand if no one chooses to), while others require it to be started immediately alongside the engine — another detail worth a quick confirmation before serious play, the same way house rules around scoring caps are worth confirming, as covered in our scoring guide.

Handling a double mid-hand

Doubles played after the initial engine get their own small convention in most rule sets: a double must generally be "satisfied" before its owner's turn is considered complete, meaning the player who plays a double typically must immediately follow it with another tile — on that same double, if possible — before passing play along. If they can't immediately satisfy it, most rule sheets mark that double the same way an unplayable train gets marked, leaving it open for anyone to play on until it's eventually satisfied. This is a lighter-weight version of the strict "every branch must be filled" rule that defines Chicken Foot; Mexican Train doesn't generally require every side of a double to be filled before play continues elsewhere, just that the double not be left dangling unsatisfied by its own player without at least an attempt.

Because this detail varies more than the engine or personal-train mechanics between published rule sheets, it's worth settling explicitly with your group — "do we require an immediate follow-up on a double, and if we can't, does it just get marked?" — before assuming everyone learned the same version.

Basic strategy for managing your own train

A few habits separate a smoothly-run personal train from one that spends half the game marked open. Don't play a matching tile onto your own train the instant it's legal if you don't have to — extending it early just gives opponents a fresh target number to try to match onto the communal train, while holding it back a turn or two keeps your options less predictable. Conversely, don't hoard so aggressively that you end up unable to move and get marked open anyway; a train that opens because you were trying to be clever, rather than because you genuinely had no play, is a self-inflicted problem.

It's also worth tracking which of your own numbers are getting scarce as the hand progresses. If you're holding two tiles that both need a particular number to play, and you've already seen most of that number's n+1 copies appear elsewhere on the layout, that's a signal to play one of those tiles at the first opportunity rather than waiting — the number you're depending on may simply not come around again. This is the same "which numbers are dead" tracking covered in more depth in our guide to defensive play and counting pips, applied here to keeping your own train moving rather than to forcing a block.

When the boneyard runs dry

Unlike a game that ends the moment the boneyard empties, Mexican Train keeps going: once there are no more tiles left to draw, a player who can't make any legal play (on their own train or the communal one) simply passes for that turn, the same way a player passes in standard block dominoes when they've got nothing to play. The hand still ends normally from there — someone dominoes, or every remaining player passes in succession and the hand blocks — it's just that drawing is no longer an option once the boneyard's exhausted. Games using a bigger set (double-twelve, with its larger 91-tile boneyard-and-hands total) tend to reach this point later in a hand than smaller sets would, simply because there's more material in play before anyone runs the boneyard dry.

Ending a hand and scoring

A hand of Mexican Train ends the same two ways as standard block dominoes: someone empties their hand (dominoes), or no player at the table has a legal move anywhere — personal trains, the communal train, or the boneyard all exhausted of options. Scoring is where Mexican Train parts company with block dominoes: when the hand ends, every player counts the pips left in their own hand and adds them to their own running total, a player who went out adds zero, and after the last hand the lowest total wins. Some groups give the double-blank a fixed penalty value; agree it before the first hand. That is the opposite of the block and draw rule in our scoring guide, where the round's winner scores everyone else's pips, so keep Mexican Train totals on a paper sheet rather than running hands through a block-scoring calculator. Because Mexican Train is traditionally played with a double-twelve set, a single hand's pip totals run considerably higher than a double-six game's — a full double-twelve set carries 1,092 total pips, more than six times a double-six set's 168, so don't be surprised by bigger score swings than you're used to from a smaller set.

Across a full descending-engine match, running totals accumulate hand after hand exactly the way they would in any other multi-round domino match — there's nothing scoring-wise unique to Mexican Train beyond the pip-total math already covered elsewhere; what's distinct about the game is entirely in how a hand is played, not how it's scored once it ends.

A quick pre-game checklist

• Confirm the set size (double-twelve is traditional, though smaller groups sometimes use double-nine).
• Decide whether you're playing a full descending-engine match or a shorter session with fewer hands.
• Agree on the double-satisfying convention — immediate follow-up required, or just marked open if not possible.
• Agree on how personal trains get marked open, and confirm anyone can play them while marked.
• Decide whether starting the communal train is mandatory alongside the engine or left optional.

None of these is a universal rule — they're exactly the kind of house-rule detail that varies from table to table, which is why settling them out loud before the first double gets placed heads off more mid-game disputes than any strategy advice could. A minute spent on this list before dealing the first engine saves considerably more time than resolving the same questions mid-hand, once opinions have already formed about how a disputed play should have gone.