40d:Traffic

Traffic may become an issue once a settlement begins to grow in size. Movement in narrow hallways is slowed by dwarves moving past each other.

Some traffic problems can be prevented by good fortress design, such as making hallway which are likely to be high use double or more width and placing stockpiles close to relevant workshops. Other difficulties may be reduced by designating traffic areas.

Vegetation (saplings) will tend to die in outdoor areas with high traffic, quickly exposing bare soil. This may be desireable as trees block dwarves' and caravans' paths, but unchecked traffic may trample entire areas of forest regrowth.

Setting Traffic Areas

The do combination sets traffic areas, which are zones 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 (default, undesignated) costs 2 points per square, Low costs 5, and Restricted costs 25. You can change these values in init.txt.

• It is often a good idea to set any water source in a biome with seasonal freezing to a Restricted area 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 wish to designate the shop as Restricted.
• If an area occasionally gets flooded, or is dangerous for some reason, routing dwarves around it could be lifesaving.
• Setting High traffic areas along roads outdoors prevents vegetation from being needlessly trampled.

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

Limitations

Traffic designations only affect path preferences when pathfinding. Dwarves generally choose their jobs without weighing the pathfinding costs. For example, one cannot use traffic designations to direct a dwarf to confine his digging to a specific area. He will still take whatever path necessary to get to the job he has chosen to work.

Additionally, traffic designations cannot be used to restrict where a dwarf will stand when building/digging. In other words, traffic designations will not prevent a dwarf from placing himself on the outside of the fort when the last tile of a moat or wall is completed. In some cases, a workaround is to place a wall where you want the dwarf to avoid standing, and suspend it. This prevents him from standing on that tile while building/digging. When the job is finished, the suspended wall may be canceled.