Underground railways perform exceedingly useful service in big traffic centres like London, Paris and Berlin. In the latter, capital work is proceeding steadily on the construction of a new underground route traversing the city from north to south, and connecting with the existing east and west railway at the Friedrichstrasse station. In length the new line is just 3 ½ miles. The tunnel is 12 ½ ft. high, and 28 ft. wide. Stations are placed at approximately 900 yard intervals, and each station is about 175 yards in length, accommodating at each platform a full-length eight-car train. As in most big European cities, surface transport has become exceedingly dense in Berlin, and the new electric underground railway should greatly relieve congestion on the roads, as well as provide a convenient means of inter-communication between the various main-line railway termini.