NotRoadTypes Spec

 

Essential

• ‘road' and ‘tram' are independent, like ‘road’ and ‘rail’

• they can coexist on the same tile in some cases, but do not influence each other

• the term ‘roadtypes’ is confusing for historical reasons and due to pre-existing use in code, and is not used here: this is NotRoadTypes

• ‘tram’ and ‘road’ are built as subtypes

• per tile, one subtype of ‘road’ and one subtype of ’tram’ may be present

• construction tools for ‘road’ and ’tram' are independent

• adding/removing/converting ‘road’ on a tile does not affect ‘tram’ for tile and vice-versa

• vehicles are either ‘road’ or ‘tram’, they cannot be both

• vehicle routing and movement per ‘road’ and ‘tram’ are independent

• any ‘road’ subtype may be freely combined with any ’tram’ subtype, there are no ways to make ‘road’ and ’tram’ incompatible with each other by subtype or any other means 

• subtypes

    ◦ proposed up to 15 ‘road' subtypes and 15 ‘tram’ subtypes (implementation detail: uses 4 bits each, uses 8 bits free in m8)

    ◦ 15 is more than enough for any game

    ◦ spec shouldn’t have an opinion on how many type a game needs, but 3 or 4 of each is plenty imho

    ◦ each subtype has a label

    ◦ vehicle compatibility with a subtype is determined by label

    ◦ vehicle may determine some properties by subtype (power, possibly others)

• drawing

    ◦ ‘tram’ is always drawn above ‘road’; authors need to be aware of this when drawing sprites, no mechanism will be provided to vary this

    ◦ drawing of city roads, bridges, tunnels, and similar will follow existing behaviour

    ◦ drawing of rail crossings may or may not be fixed (road tile is enforced for tram crossings currently, this looked non-trivial to fix when I tried)

    ◦ methods _may_ be provided to enable more control over appearance, e.g. snow above snowline etc

• catenary

    ◦ subtypes can provide catenary, or not (implementation detail: flag or cb returning sprites)

    ◦ both ‘road’ and ‘tram’ can provide catenary on a tile

    ◦ authors will need to draw catenary carefully to avoid it looking bad when ‘road’ and ‘tram’ catenary are combined on a tile

    ◦ vehicle power on a tile is determined by vehicle against subtype label, unrelated to drawing of catenary sprites

    ◦ there is sophisticated handling of rail catenary to preserve continuity where railtypes cross, something similar needs to be provided for NotRoadTypes

• converting between subtypes

    ◦ a convert tool is needed, similar to rail conversion

    ◦ this will need to consider ownership carefully

        ▪ too restrictive = can’t overbuild subtypes in towns

        ▪ too permissive = deliberate or accidental breaking of existing routes by overbuilding incompatible subtype

• drive-in stops:

    ◦ behaviour of articulated vehicles and trams unchanged, can’t use drive-in stops

    ◦ catenary needs to be provided for ‘road' drive-in stops

• overtaking: out of scope

 

Optional (proposed by frosch)

• split global toolbar to ‘road’ and ‘light rail’

• this makes the distinction between the transport types obvious

• in this way it’s clear that a tile can have

    ◦ 1 type of rail

    ◦ 1 type of road

    ◦ 1 type of light rail

• unknown: would the various vehicle menus, station menus etc also be split for ‘road’ and ‘light rail’?