if (already_reversed && prev->tile != tile) {

			/*

			 * The vehicle has reversed, but did not go straight back.

			 * It immediatelly turn onto another tile. This means that

			 * the roadstate of the previous vehicle cannot be used

			 * as the direction we have to go with this vehicle.

			 *

			 * Next table is build in the following way:

			 *  - first row for when the vehicle in front went to the northern or

			 *    western tile, second for southern and eastern.

			 *  - columns represent the entry direction.

			 *  - cell values are determined by the Trackdir one has to take from

			 *    the entry dir (column) to the tile in north or south by only

			 *    going over the trackdirs used for turning 90 degrees, i.e.

			 *    TRACKDIR_{UPPER,RIGHT,LOWER,LEFT}_{N,E,S,W}.

			 */

			Trackdir reversed_turn_lookup[2][DIAGDIR_END] = {

				{ TRACKDIR_UPPER_W, TRACKDIR_RIGHT_N, TRACKDIR_LEFT_N,  TRACKDIR_UPPER_E },

				{ TRACKDIR_RIGHT_S, TRACKDIR_LOWER_W, TRACKDIR_LOWER_E, TRACKDIR_LEFT_S  }};

			dir = reversed_turn_lookup[prev->tile < tile ? 0 : 1][ReverseDiagDir(entry_dir)];

		} else {

			dir = (Trackdir)prev_state;

		}