# 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 requires the player to select its uphill direction; v0.4.5 instead selects that direction from the game seed during setup. 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 requiring correction

`src/engine/content.ts` defines nine `MAINLINE_PROFILES` types: one Plains entry plus the eight other terrain types above. `setup.ts` selects uniformly from that nine-type list. The second Plains card shown in `Mainline Cards.pdf` is therefore not represented as a duplicate card or as extra Plains weight in setup. If the PDF inventory is authoritative, the setup selection needs a second Plains entry (or an equivalent weighted selection).

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 finite draw pile, player choice, or physical placement interaction for Mainline cards; setup selects their types automatically from the seeded random stream.
- 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.
- Heavy Grade orientation is seeded automatically rather than chosen by a player. The implementation needs a player-selection step to match the card.