explanation: underground pipe systems are 1D graphs. adding time, the vertical (Y) axis starts from "now" and goes into the future. as the track is a loop, this graph is actually a cylinder, and a robot's mission is a series of line segments drawn on the surface. a waiting robot is a vertical line. moving at a constant speed is a diagonal line, and acceleration is a curved line. deconfliction simply becomes a puzzle.
robots in underground pipes provide many enjoyable opportunities for path optimization