Air Resistances to Trains in Tube Tunnels

The development in recent years of tube tunnels and subways with close clearances, as integral parts in the construction of high-speed, electrically-operated railways for passenger transportation, has opened questions of somewhat serious moment in the operation of such lines, which had not previously been considered, although under these new conditions they have a material bearing on the operation, and should have some consideration in the design under which such tunnels are constructed. An interesting question of this character, regarding which, as far as the writer can find, little information has been published or is available, is that of the resistance of air and the movement of columns of air in the operation of trains in tube tunnels.