For as long as man can remember - animators have been trying to avoid animating cars

In order to save costs, the 101 Dalmatians production team thought up an inventive way to animate the vehicles seen in the 1961 movie. Instead of drawing the vehicle frame by frame the conventional way, a cardboard model was filmed, as effects animators moved it around in front of the camera. Note the black lines that define all edges.

Frames from this live-action footage were xeroxed on to cels before being painted in the ink & paint apartment. The same process was used later on for Edgar’s motorcycle in The Aristocats.

The equivalent in 2D digital animation today would be to model and animate the vehicles in a 3D computer-generated environment, render it out, import them into the 2D animation software and trace over it frame by frame.

Source.