A hundred years ago, wartime conditions in England were such that there weren’t sufficient liquid fuels (gasoline or methyl alcohol) to run the buses. Undaunted, they switched to the same gas that was used to run the streetlights, conveniently stored in rooftop bags, as shown on the cover of the October 1917 issue of Popular Mechanics.
Complete information was apparently not available to the editors of the American magazine, since they noted that “the amount of power obtained from the lighting gas depends upon a number of things, and a reliable estimate could not be made without more detailed information thanis at hand. It is also not altogether clear why unwieldly bags are being used instead of compact steel cylinders which could carry gas under high pressure.”
But since the streets were already wired for gas, adding filling stations along the route was a minor matter. Indeed, some of the filling stations consisted merely of existing lamp posts situated near the curb.