Today we’ll be exploring the Green Line’s D branch. The D, running from Kenmore to Riverside, has one of the most unique, convoluted histories of all the T’s lines, evolving from an intercity steam railroad into a modern subway line.
Today’s D is composed of several separately built segments. The line first opened in 1848, when the short Brookline branch was built from today’s Worcester Commuter Rail line at Kenmore to Brookline Village — the first transit to serve Brookline. Before it even opened, this branch was supposed to extend all the way to Rhode Island. To do so, it was first extended to Newton; from there, it split from today’s D, running southwest to Needham and then all the way to Woonsocket, RI.
The D would reach its full length in 1886, when a connection was built from Newton to the Worcester Line at Riverside. To make things even more complicated, in 1906, today’s Needham Commuter Rail line was connected to the Newton-Rhode Island segment in Needham.
At its climax, several types of trains ran on the D. Early traffic included intercity and freight trains, including trains carrying stone from Needham to fill in the then-marshy Back Bay. However, commuter traffic would become the line’s bread and butter, running via two massive loops. Some trains would run over the entire D to Riverside, then loop back into Boston via the Worcester Line. Others would take the “Needham Circuit,” splitting from the D at Newton and looping back into Boston via the Needham Line.
After World War II and with the rise of the automobile, these commuter trains lost customers faster than post-rebrand Carm. Instead, commuters drove in droves into Boston over modern — but increasingly congested — highways. The government, faced with overutilized highways and an underutilized rail line, decided to kill two cars with one train by converting the D into a modern mass transit line.
The D would be converted to electric light rail operation and connected to the Green Line. In keeping with the zeitgeist, stations boasted massive park-and-ride lots, where suburban commuters would transfer between car and train. Funding was low, so simple stations were erected and track upgrades were minimized, leading to rough, bouncy rides. No new trains were purchased; instead, streetcars were transferred from Harvard, being replaced by trolleybuses that still run today.
The project was completed in 1959, ahead of schedule, under budget (the first time I’ve written those words) and instantly successful. D ridership increased tenfold; it’s estimated that the line reduced rush hour downtown congestion by 7%. The D stands as proof that if you build fast, frequent and convenient transit, the riders will come.
Today, the D is the longest, busiest and perhaps most unique Green Line branch — originating as a railroad and not a streetcar line, it boasts high speeds, car-free tracks and a scenic, wooded route. It’s been continuously upgraded to handle increased ridership (and compensate for lack of initial investment), with still more upgrades proposed. Some have even proposed connecting the D to the Blue Line, going all the way to Wonderland.