Train appears at 2:11 in the clip, for those interested in seeing it

The general type of vehicle is called a draisine, they are a common service vehicle on railroads. If you do an image search you can find open and covered versions.

Lots of back-country railroads and branch lines around the world had too little traffic for the overhead of a steam locomotive pulling a couple of cars, which typically required a staff of at least three. When the internal combustion engine became commonplace, many railroads built or purchased lightweight single coaches that were powered that way; many of them just resembled a large touring auto or small bus on railroad wheels. Because so many of these were built in the railroads' own shops, design varied and some were pretty homely.

After World War II, Budd built RDC cars, cars self-propelled by center mounted diesel engines, that were used by many North American railroads for low-traffic branch lines, and some suburban services. RDCs could be coupled together into short trains, something not practical with earlier "rail-buses." Several of these are still in service around the world; last year I rode a train of such cars (from another builder) from Bangkok to Chiang Mai.