Path planning at roundabouts using piecewise linear continuous curvature curves

The number of roundabouts has been increased as they have demonstrated improvements over unsignalized and signalized intersections regarding safety, traffic flow, access management, etc. In this sense, autonomous vehicles should satisfactorily deal with the problem of path planning at these circular intersections. Approaches proposed in literature employ optimization techniques to improve the level of comfort and to ensure bounded curvature subjected to the vehicle's kinematic constraints. This paper describes a path planning approach for autonomous vehicles using clothoids, circular arcs, and straight lines, whose curvature is piecewise linear and continuous as well. The planned path provides smooth driving because of the linear variation of the curvature with respect to the traveled distance. The roundabout path planner interpolates the desired configurations of the vehicle at roundabout entrance and exit with G
²
continuity as traveling along the circular roadway. The proposed approach was tested on real and simulated doublelane roundabouts and results demonstrate the effectiveness of the path planning, which ensure bounded curvature and low curvature derivative, providing driving comfort.