Likewise with steam railway, engineers were also interested in using compressed air as a source of power for locomotives. It was even believed that vehicles propelled by compressed air could be seriously competitive to steam locomotives. The first projects appeared in the United Kingdom but they were not a commercial success at that time. However, works to develop such solutions were continued. One of the first locomotives propelled by compressed air which was successfully used was built by Baldwin Locomotive Works in 1877. The vehicle was small, had a single tank and from 5 to 10 inch cylinders.
In 1883 compressed air was used to power the machinery at a colliery near Freiberg in Germany, where as early as 1891 cargo was transported by pneumatic locomotives. The route was approximately 1000 m long. The locomotive was mounted on two pins on a four-wheeled bogie to make it flexible. Air was supplied to the locomotive under the pressure of 12 (empty) or 18 atmospheres (loaded).
Compared with steam locomotives, an advantage offered by pneumatic locomotives is the lack of exhaust and smoke. In addition, they had no furnace so they could operate in potentially explosive conditions. It was even claimed that the use of compressed air in locomotives was good for ventilation and it supplied fresh air to mine headings. Thus, it was used during the construction of a tramway line in New York for tunnelling works and for transportation in the mines.
In some mines electric locomotives superseded pneumatic locomotives, but they are still in use in many, in particular in the United States. Production of this type of traction has been a major part of the activities of leading railway companies, in particular Baldwin Locomotive Works of Philadelphia, the American Locomotive Company of New York, or HK Porter Company of Pittsburgh. The cost of construction of vehicles propelled by compressed air is competitive in comparison to electric locomotives.
Pneumatic locomotives can be charged directly from a compressor, but this is not an efficient type of supply. It is much better to install a reservoir at a convenient location in the mine from which the vehicle's tank could be easily charged. This way the compressor works in a continuous manner restoring normal pressure required to propel the locomotive while the latter is in operation. Sometimes air is also supplied via pipelines with no need to build and install stationary compressed air tanks.