Shadows in the singular metric

Four examples of shadows (dashed region) of a segment obstacle (green): the shadows are defined as the sets of positions (x,y) in the plane reachable from the configuration (0,0,0) of the car by a shortest path colliding the segment.
(The white curves define the partition of the plane according to the shape of the shortest paths reaching a position (x,y); see P. Souères, J.Y Fourquet and J.P. Laumond, "Set of reachable positions for a car", IEEE Trans. on Automatic Control, 39 (8), 1994.)

See :

...and what happens if the car should move only forward ?...