3ds Max Modeling :: Trajectories Are Virtually Identical In Shape And Number Of Points

I've got two trajectories from the bottom of two tires and I want to create a road surface, an object whose shape will match the trajectories, thereby creating a perfect shadow catcher.

The trajectories are virtually identical in shape and number of points because the two point helpers that created them were wired together. I've converted them into splines and messed with the loft tool, with not so good results. I ended up brute forcing the shape of the object into some kind of shape but I think there has to be a good, dependable way to do this in a program like max.