Not sure how roads are one-dimensional. If that was the case, then collision always happens when two points are on the same distance from beginning of the road.

Not sure how roads are one-dimensional. If that was the case, then collision always happens when two points are on the same distance from beginning of the road. But I somehow manage to make it from A to B on a highway together with other cars. Roads are two-dimensional for collision calculations. Air is three-dimensional: you can be at the same latitude and longitude, but separated by elevation.