# Station Master — Mainline Deck

**Rules implementation reference: v0.4.5**  
**Scope:** the tarot-sized Mainline cards placed between Offices. This is an implementation reference, not a transcription of earlier prototype rules.

## How Mainline cards work

At setup the game places one randomly selected Mainline card between each neighbouring pair of Offices and one beyond each end Office, between it and a Division Point. Thus, a game with *N* players has *N + 1* Mainline cards. The implementation selects types with replacement; it does not deal them from a shuffled finite deck.

A train crossing a Mainline card spends Stages, rather than moving through its printed cells. A 60 mph card costs one Stage and a 30 mph card costs two. A Slow train adds one Stage to every crossing. On Hilly terrain, any train carrying at least one coach uses the passenger rate; a train carrying no coach uses the freight rate. No crossing can take less than one Stage.

The card does not itself determine which player owns the adjacent Office. It is part of the shared Division.

## Physical card inventory in `Mainline Cards.pdf`

The supplied PDF has **ten** tarot-sized terrain cards. Plains appears twice; the other terrain types appear once each. It also includes two Division Point cards.

| Physical card | Copies in the PDF |
| --- | ---: |
| Plains | 2 |
| Curves | 1 |
| Hilly | 1 |
| Heavy Grade | 1 |
| Double Track | 1 |
| Uncontrolled Siding | 1 |
| Tunnel | 1 |
| Trestle | 1 |
| Interchange | 1 |
| East Division Point | 1 |
| West Division Point | 1 |

The PDF art labels this card “Yard”; this reference uses the implementation’s correct name, **Interchange**, to distinguish it from the Division Yard, Classification Yard, Yard Office, and Small Yard.

## Implemented Mainline card reference

| Card | Implemented crossing time and feature |
| --- | --- |
| Plains | 60 mph; one Stage for Fast, two for Slow. The implementation has one Plains *type* rather than the PDF’s two physical copies. |
| Curves | 30 mph; two Stages for Fast, three for Slow. |
| Hilly | Passenger train: 60 mph. Freight-only train: 30 mph. Add one Stage if Slow. |
| Heavy Grade | Starts at 30 mph; two Stages for Fast, three for Slow. The card prints “Player sets orientation”; **the game deliberately overrides that and rolls the uphill direction from the seed** — settled in v0.5.0 and re-confirmed 2026-08-23, see the note below. Grade modifiers can reduce the time, to a minimum of one Stage. |
| Double Track | 60 mph. Printed capability: trains may pass. The traffic-resolution rule is in Rules §4.5. |
| Uncontrolled Siding | 60 mph. Printed capability: trains may pass. The traffic-resolution rule is in Rules §4.5. |
| Tunnel | 30 mph. |
| Trestle | 60 mph. |
| Interchange | 60 mph. A train may be reordered there only through the card’s printed “sort cars” concept; the current engine does **not** provide a Mainline sorting action for it. |

### PDF/code mismatch — CORRECTED

**Was:** `src/engine/content.ts` defines nine `MAINLINE_PROFILES` types: one Plains entry plus the eight other terrain types above. `setup.ts` selected uniformly from that nine-type list, **with replacement**. The second Plains card shown in `Mainline Cards.pdf` was therefore not represented as a duplicate card or as extra Plains weight in setup — and, worse than a weighting error, a Division could be dealt two Interchanges, two Tunnels or two Trestles, none of which the deck contains.

**Now:** `MAINLINE_DECK` in `content.ts` is the inventory table above — ten drawable cards, Plains twice and the other eight once each — and `buildDivision` deals from it without replacement. The two Division Point cards are not in that deck: they are the fixed ends of the Division, laid by `buildDivision` itself rather than drawn.

The Interchange is what forced the correction. §7 lets an Extra be started at the Interchange "if one is on the board" (see `docs/rules/implications.md`, §7), which only reads as a rule if the board can hold at most one.

The executable state represents East and West Division Points as fixed end nodes, not as card records. They are functionally present at the ends of the Division, but are not represented as the two PDF cards in the deck/state model.

## Heavy Grade modifiers

These cards come from the Home Office deck and are played onto a Mainline card during a player’s Draw option.

| Card | Copies | Placement and actual effect |
| --- | ---: | --- |
| Brakeman | 1 | Heavy Grade only. Reduces a downhill crossing by one Stage. |
| Airbrakes | 1 | Heavy Grade only, and Brakeman must already be on that card. Reduces a downhill crossing by one additional Stage. |
| Helpers | 1 | Heavy Grade only. Reduces an uphill crossing by one Stage. |
| Realignment | 2 | May be played only onto an unoccupied Mainline card. Changes Plains → Double Track, Curves → Plains, Uncontrolled Siding → Double Track, or Trestle → Uncontrolled Siding. It cannot be played on any other card type. |

For the grade cards, “uphill” should be the direction selected by the player when the card is placed. In v0.4.5 it is the seeded `gradeUp` direction because setup has no player-choice step.

## What is not implemented

- There is no player choice or physical placement interaction for Mainline cards; setup deals them automatically from the seeded random stream. There **is** a finite draw pile as of v0.6.2 — the deck above, dealt without replacement, so no Division can hold two of a card printed once.
- Interchange is catalogued as a “sort cars” card, but v0.4.5 has no operation that reorders a train on the Interchange. The Small Yard in an Office Area is the implemented sorting mechanism.
- Interchange now has one player-facing use: an Extra Train may be **started** there, made up in its yard and highballing onto the Mainline when the Subdivision is clear (§7, v0.6.2). Car sorting remains unimplemented.

## Heavy Grade orientation is settled, not missing

Heavy Grade orientation is rolled from the seed rather than chosen by a player. **This is a decision, not a gap, and it is not awaiting a player-selection step.**

The card prints “(Up)” and “Player sets orientation”, which assumes the card has an owner. This one does not: `buildDivision` lays the Division as `DP · Mainline · Office · Mainline · … · DP`, so a Heavy Grade always sits **between two districts**, or beyond an end Division Point next to one — never inside a single player’s own district.

Orientation is not cosmetic: Brakeman and Airbrakes each take a Stage off a train running **downhill**, Helpers takes one off a train running **uphill**, and odd-numbered trains run west while even run east. Turning the card around therefore decides which of those modifier cards are worth anything and which direction of traffic is favoured — permanently, for the whole game. Handing that to one of the two neighbours advantages them over the other, and no player has a fair claim to it.

**Re-opened and closed again on 2026-08-23**, when the option of giving the choice to the Superintendent was considered and rejected. Jesse’s call: v0.5.0’s ruling stands. Rolling from the seed is deterministic, roughly even (51/49 east/west over 400 games), identical for solitaire and multiplayer, and keeps setup non-interactive — the game has no setup phase, so the question would have to interrupt play before the first Local Operations, in the minority of games that deal the card at all (20% at one player, rising to 50% at four).