EXTRA-FREEDOM STITCH METHOD FOR REFERENCE LINE SMOOTHING

In one embodiment, a method for generating a reference line for operating an autonomous driving vehicle includes controlling an autonomous driving vehicle to move along a road according to a first reference line, the first reference line having a first set of constraints, and while the autonomous driving vehicle is moving along the road according to the first reference line: truncating the first reference line by removing an end section of the first reference line to generate a truncated first reference line including an end reference point, obtaining a second set of constraints for the end reference point, obtaining a second reference line to be used by the autonomous driving vehicle, the second reference line having the first set of constraints, and connecting the second reference line to the end reference point of the truncated reference line to allow the autonomous driving vehicle to move along the road.