Fourth component layout: 3-Wheelers witch include parts that lean sideways in curves in order to avoid the rollover problem presented by many 3-Wheelers.

Lots of such 3-Wheelers incorporating different leaning systems have been developed. Among them, there were the Gm Lean Machine and the Mother Earth 3VG:

The Mercedes F-300 appeared more recently:

In all these cases, an additional mechanism was added that increased the complexity and weight of the vehicle to resolve the rollover problem.

This 3-Wheeler component layout incorporating a leaning system might not be eliminated totally, but it has yet to be proved that simple, failsafe and cheap leaning system can be developed to be put in the hands of the general public.