In this paper, we present a general theory of motion planning for kinematic systems. In particular, the theory deals with epsilon-approximations of non-admissible paths by admissible ones in a certain optimal sense. The need for such an approximation arises for instance in the case of highly congested configuration spaces. This theory has been developed by one of the authors in a previous series of papers. It is based upon concepts from subriemannian geometry. Here, we summarize the results of the theory, and we improve on, by developing in details an intricate case: the ball with a trailer, which corresponds to a distribution with flag of type 2, 3, 5, 6.