The Forest Hills-Everett route is called the main line, and the Harvard-Andrew route the Cambridge Subway. The Bowdoin-Maverick Square line up to the present has been operating three-car trains with overhead trolley, but new equipment consisting of steel cars is now on order and the third rail is now being installed in the tunnel. The Lechmere Sq.-Broadway line over East Cambridge Viaduct and Tremont St. Subway is also considered a rapid transit route, although surface type cars are used with overhead trolley. These cars are equipped for multiple unit control and are operated in three-car trains.
35,000-Kw. Turbo-Generator in South Boston Power Station
The rush hour trains on the main line include as high as eight cars, which is the limit set by the length of the station platforms. The signal system is entirely automatic and during rush hours the headway varies from 2 to 3½ minutes on the main line. The maximum grades encountered are 2 to 3 percent with a high percentage of heavy curvature. By taking advantage of the transfer arrangements at terminals, rides of 14 miles can be obtained for a single fare.
Power Station Equipment
The power system as originally installed included several engine-driven direct-current plants suitably located for distributing 600 volts direct to the trolley. With the extension of the system, however, an alternating-current station was installed at South Boston, generating 25-cycle three-phase current for distribution at 13,200 volts to synchronous converter substations. Alternating-current generating equipment has also been installed at the Lincoln Station. The total installed capacity of turbine stations is now 115,000 kw. while the direct-current generating stations have practically all been discontinued.
Rapid Transit Lines—Boston Elevated Railway
Exterior of Egleston Square Substation