Editing Loading gauge (section)

====Boston (MBTA)====
The [[Massachusetts Bay Transportation Authority]]'s (MBTA) rapid transit system is composed of four unique subway lines; while all lines are standard gauge, inconsistencies in loading gauge, electrification, and platform height prevent trains on one line from being used on another. The first segment of the [[Green Line (MBTA)|Green Line]] (known as the [[Tremont Street subway]]) was constructed in 1897 to take the streetcars off [[Boston]]'s busy downtown streets. When the [[Blue Line (MBTA)|Blue Line]] opened in 1904, it only ran streetcar services; the line was converted to rapid transit in 1924 due to high passenger loads, but the tight clearances in the tunnel under the [[Boston Harbor]] required narrower and shorter rapid transit cars.<ref>{{cite book| last = Clarke| first = Bradley| title = The Boston Rapid Transit Album| publisher = Boston Street Railway Association| year = 1981| location = Cambridge, Mass.| page = 8}}</ref> The [[Orange Line (MBTA)|Orange Line]] was originally built in 1901 to accommodate heavy rail transit cars of higher capacity than streetcars. The [[Red Line (MBTA)|Red Line]] was opened in 1912, designed to handle what were for a time the largest underground transit cars in the world.<ref name=Fischler>{{cite book|last1=Fischler|first1=Stanley I.|title=Moving millions : an inside look at mass transit|date=1979|publisher=Harper & Row|location=New York|isbn=0-06-011272-7|edition=1st|url-access=registration|url=https://archive.org/details/movingmillions00stan}}</ref>{{rp|127}}