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5.3 Impossible Changes

This is a list of things I'm regularly asked to do, but which are either impossible to do, or at least an awful lot of work:

• Higher bridges. Complication: TTD has no provision to store the height of a bridge, it is always implicitly one, nor can the graphics engine display them.
• Diagonal bridges or tunnels, for the same reason.
• More cargo types. This can't be done because there can only be 12 different cargo types per climate, and it's impossible to add more.
• More stations or more depots.

  Both stations and depots have an ID value that is stored in a single byte in memory. Because of this, the IDs can only go up to 255, allowing at most 256 stations or depots. For stations, a couple of the ID values have special meanings, so that only 250 stations are possible.

  However, because they are stored in a byte, it is not possible to have more stations or depots than 255. It is all but impossible to change the ID to use a word value, which would be required to do that.

  Changing the number of vehicles on the other hand was less difficult because they were already stored in a word value, which can take values up to 65535.

• Joining more than one of each station facility type in a single station, e.g. two joined bus stations. While it is possible to place those on the map, the internal station structure can only hold the position of one of each facility type. Therefore the vehicles would only use one of them as well. In addition this would eventually turn into a ghost station.
• Larger airports (more runways). It's possible, but would involve recoding the whole aircraft movement scheme of an airport. It's too much work right now. Maybe if enough people bug me about it I might do it though. If/when I do it, I'd add another runway at the other side of the airport, and separate them into landing/departing runways. This should work nicely, but it is still a lot of work.
• Larger maps. This is all but impossible, because the whole program assumes a coordinate has 8 bits for each direction, totalling a 256x256 grid.
• A patch for the original Transport Tycoon. I have worked on TTDPatch for almost six years now, and asking me to duplicate that work for TT original is just a little bit unreasonable.
• More players in multiplayer games. This would need a full re-write of TTD's multiplayer networking protocol. That's pretty much impossible without having the source, and even then it would be a huge amount of work.