3-wheelers were quite common in the UK, Germany and Italy in the 1950s, 1960s and maybe a little bit in the 1970s. Reliant was one of the best known UK makers, also better known by Britcar fans for the later 4 wheel Scimitar.
In general they were all found to be fundamentally dangerous to drive, especially on wet roads, and they died out. There were both types, two wheels in front, and two wheels behind - both were death-traps.