In the late 1910s, interest in a self-propelled coach grew enough that several companies began producing them. They were used primarily on small branch lines for service where it did not make financial sense to run a full locomotive. Most had a gasoline engine driving a generator, while some had a gasoline engine connected to a truck via a transmission or even direct drive. They could tow one unpowered car. Doodlebugs could be seen for decades scampering back and forth between cities and outlying areas, operated by small rail companies. They helped connect small towns and villages to city centers and, in doing so, helped connect America.
In the buildup to WWII, many Doodlebug builders and operators went out of business or retooled for wartime production. The larger railroads, flush with cash from the military, started offering more services to areas served by the Doodlebug to get recruits and draftees where they needed to be.
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