Trajectory of a reversing/backing vehicle?

When a vehicle is reversing/backing (typical maneuver during parking, and sometimes cars do that on freeways..), is there any way to describe in Trajectory? I am thinking of adding an optional parameter "orientation" to describe the attitude of a vehicle for each vertex/control point. And the movement between these points can be interpolated. If no "orientation" is defined, the vehicle will have heading angles aligned with tangent direction of the poly-lines defined in trajectory. Any input/comments/suggestions are welcome.