Chicago streetcar – or is it?

The Chicago tram system (or streetcar system, to use the proper American term) started with horse-drawn trams in 1859, and grew to cover 500 miles of electrified routes by 1935. At its height the system used 3,700 red streetcars, but by 1958 they had been replaced by electric “trolley buses”, which got their power from overhead cables like streetcars, but had the advantage of not being tied to tramlines in the road surface. Motor buses were even more flexible, and the last Chicago streetcar ran in 1958.
At first glance this picture appears to show a typical historic tram or streetcar. But look more closely and it is clear it is not: above it lacks the articulated arms used to pick up power from overhead cables, and below it doesn’t have the bogey wheel structures needed to run on rails. In fact it looks like this vehicle runs on conventional bus wheels, presumably having its own source of power, such as a diesel engine.
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