Homotopic-based planner for autonomous vehicles

Among other things, techniques are described for planning a route for an autonomous vehicle. As an example, a set of candidate constraints for a road segment to be traversed by a vehicle is obtained. A plurality of homotopies are determined, each including a different respective combination of the candidate constraints. For each homotopy, a first prediction of a motion of the vehicle is generated according to a first degree of precision, and a determination is made that the vehicle can traverse the road segment according to a subset of the homotopies. Further, a plurality of trajectories are determined according to the subset of the homotopies, including generating at least one second prediction of the motion of the vehicle according to a second degree of precision greater than the first degree of precision, and selecting one of the trajectories.