In this paper, we present a method for finding the closed form solutions to the problem of determining the pose of a camera with respect to a given set of parallel lines in 3D space from a single view, while it can not be solved by previous methods for the perspective-n-line (PnL) problem. The main idea of our method is that, firstly the distances from the optical center of the camera to these parallel lines are determined, and then the pose parameters are recovered using the obtained distances. The problem of finding these optical-center-to-line distances in fact is the degenerated perspective-n-point (PnP) problem, and we proved that there are at most two solutions for the degenerated P3P problem. An application of our method is to distinguish crosswalks and staircases aiding for the partially sighted. The method also provides a different way to investigate the problem of shape from texture.