A path planning method for road networks having turn prohibitions

In metropolitan areas, intersections having turn prohibitions are often found and should be taken into account in path planning. This paper presents a new path planning method for road networks having turn-prohibitions. A road network model is proposed in which alternative routes for turn-prohibitions are prepared using U-turns or P-turns. The proposed network model is efficient since it requires no additional virtual nodes that are usually used in the conventional road networks to represent turns at intersections. In order to find a shortest path with the proposed network, a new shortest path algorithm is proposed. A knot for the turn-prohibited node is newly defined and is utilized to compare the cost of the alternative route to that of the other path. A number of experiments were performed on a real road network. Experimental results show that both the database size and the computation time of the proposed scheme are less than half of the conventional path planning method.