1. A computer-implemented method, comprising: receiving a location of a plurality of detected points on a roadway in an environment of an autonomous vehicle; determining, from a prior map of the roadway, a location of a plurality of reference points from a boundary marker on the roadway that correspond to the detected points on the roadway; determining distances between the detected points and the corresponding reference points based on the location of the detected points in the environment and the location of the reference points from the prior map of the roadway; determining a confidence buffer representing a threshold amount of variation associated with the prior map based at least in part on the distances between the detected points and the corresponding reference points; selecting one or more of the detected points such that the distance between a selected detected point and a corresponding reference point is less than the confidence buffer, wherein the selected points are a current representation of the boundary marker on the roadway; and using the selected points to direct the autonomous vehicle along the roadway.