Philosophy

• The complex fabric of real road geometry goes beyond "streets" and "intersections", which at best can be understood as loose groups of related lanes (EMERGENCE, ACTUAL PROBLEM)

Design Decision

• The atomic unit of road geometry in Citybound is the individual lane.
• Roads and intersections are just collections of lanes (EMERGENCE, FLEXIBILITY)

Implementation Philosophy

• Really make individual lanes the main abstraction, only group them into higher abstractions when absolutely necessary.
• If possible, only handle a group of "nearby/related" lanes temporarily while using a tool
• Also see Road Planning

Implementation Decisions

• Each lane keeps track of
  • it's connectivity to preceding/following lanes (connected to it's start or end)
  • lanes it overlaps, distinguishing between nearly-parallel overlaps and opposing overlaps
• Special case: two parallel lines that can be merged between are not directly connected
  • instead, an invisible "switch lane" is placed along their range of overlap
  • the lanes on either side have a special parallel overlap relation ship to the switch lane only, not to each other.
  • the reason for this is that merging car behaviour is a more complex special case
• Also see Car Microtraffic