Structs
This is cheaper to store than a MovementID. It simply indexes into the list of movements.
A Movement groups all turns from one road to another, letting traffic signals and pathfinding
operate at a higher level of abstraction.
A movement is like a turn, but with less detail – it identifies a movement from one directed
road to another.
One road usually has 4 crosswalks, each a singleton Movement. We need all of the information
here to keep each crosswalk separate.
Functions
find_r 🔒