A new contributor "Z303" sends in this picture of a SmartCar OV58SKJ showing why they are invaluable in a city, here Devonshire Road, Redland.
There is no way you have been able to park a normal car in such a narrow gap between the car in front and the tree. By parking diagonally, wheels slightly on the pavement -but not enough for a pedestrian to notice- the back of the car does not stick out into the road. This means it hampers normal traffic flow much less than a full-on sideways park. Slick.