NotRoadType Spec

Essential
• split RoadType to StreetType and TramType
• per tile, one StreetType and one TramType may be present
• they can coexist on the same tile in some cases, but do not influence each other
• construction tools for StreetType and TramType are independent
• adding/removing/converting StreetType on a tile does not affect TramType for tile and vice-versa
• subtypes
    ◦ up to 15 StreetType subtypes and 15 TramType subtypes (implementation detail: uses 4 bits each, uses 8 bits free in m8)
• drawing
    ◦ (lowest) Ground -> StreetType -> TramType -> Sidewalks + Decoration -> StreetTypeCatenary -> TramTypeCatenary (highest)
    ◦ 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
    ◦ both StreetType and TramType can provide catenary on a tile (implementation detail: flag or cb returning sprites)
    ◦ 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 current subtype in towns
        ▪ too permissive = deliberate or accidental breaking of existing routes by overbuilding current subtype
• drive-in stops:
    ◦ behaviour of articulated vehicles and trams unchanged, can’t use drive-in stops
    ◦ catenary needs to be provided for StreetType drive-in stops
• vehicles
    ◦ vehicles are StreetType XOR TramType (bool flag)
    ◦ each subtype has a label
    ◦ vehicle compatibility with a subtype is determined by label
    ◦ vehicle may determine some properties by subtype (power, possibly others)
• overtaking: out of scope
• newgrf author considerations
    ◦ user should be able to see whether catenary exists for road, tram, or both
    ◦ authors will need to draw catenary carefully to avoid it looking bad when StreetType and RoadType catenary are combined on a tile

Optional (proposed by frosch)
• split global toolbar to ‘road’ (StreetType) and ‘light rail’ (TramType)
• 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’?