A confidence value is determined for data collected for a lane assist subsystem in a vehicle. A section curvature is identified for a section of a roadway when the confidence value is below a confidence value, threshold. The section curvature includes at least one section start point and at least one section end point. The section curvature is based at least in part on a heading angle, the heading angle defining an angle between a projected line of travel of the vehicle and a line segment from a vehicle position to the section end point. A distance to a lane boundary is predicted based at least in part on the identified section curvature. One or more vehicle subsystems is actuated based at least in part on the predicted distance to the lane boundary.