/*! \brief Reeds & Shepp (build) and Euclidean + abs angle (search).
*
* Use Reeds & Shepp path length for building tree data structure and Euclidean
- * distance plus (abs) heading difference for searching it.
+ * distance + (abs) heading difference + 0.1 * backward-forward direction
+ * changes for searching it.
*
* \ingroup ext-cost
* \see https://doi.org/10.1109/TITS.2015.2477355