40d:Traffic

The do combination sets traffic areas, which are used to manipulate the movements of dwarves. Traffic areas can be designated as high, normal, low or restricted. When walking from one point to another, dwarves consider these designations in finding the shortest path. High level traffic costs the pathfinding AI 1 point per square, normal (the default, and unmarked) costs 2 points per square, low costs 5, and restricted costs 25. You can change these values in init.txt.

Setting Restricted does not forbid a dwarf from traveling over those squares, but rather makes them willing to walk around them – for the normal cost table, 12.5 times further, or up to 25 times longer if there is an alternative high-traffic path.

Vegetation will tend to die in outdoor areas with high traffic, eventually exposing bare soil.

• It is often a good idea to set any water source in a biome with seasonal freezing to restricted so your dwarves will be less likely to be caught on it when it melts.
• Some dwarves get disturbed if they walk through a butcher's shop and see an animal being slaughtered, so you may with to designate as restricted the shop.
• If an area occasionally gets flooded, or is dangerous for some reason, routing dwarves around it could be lifesaving.
• Designating paths in certain areas may help vegetation grow that would otherwise be trampled.

If you have an area that absolutely must not be stepped on by dwarves, consider walls.