In the early 1930s,  small railway operations were looking for ways to cut expenses. One effort to do that resulted in the development of the "Doodlebug".  This involved the conversion of a passenger car into a motorized railway car.  Typically a Model T engine would provide the power and would be fitted to an extended frame of a  car by the railway shop. With the addition of a headlight and of course a bell, you had a pretty economical unit. In the 1950s the concept was rejuvenated in the form of the Rail Diesel Unit (RDC). 

My model was made in a similar fashion using a motorized truck just like I did on the Toonerville Trolley.  That's one helluva bell hanging out there! 

Doodlebug,  circa 1930

Rail Diesel Unit,  circa 1950

Doodlebug at Martini Junction,  circa 2020