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; 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 a confidence buffer; adjusting the confidence buffer based on a percentage of the detected points that were not selected; and using the selected points as a current representation of the boundary marker to direct the autonomous vehicle along the roadway.