Offset curves of clothoidal splines

Abstract Offset curves are important in some aspects of computer-aided design. Several authors have studied, and found, approximations to offset curves of cubic B-splines. Curves made of segments of clothoid spirals, arcs of circles, and straight line segment are used as centre lines of railways and highways, and offsets of these curves are used for rail or shoulder lines. This note points out that offsets of these curves are not much more complicated than the curves themselves, and can be rendered efficiently on a plotting device.