Boston-area trackless trolleys
The Massachusetts Bay Transportation Authority manages four trackless trolley routes in Boston, Massachusetts, operating in the Harvard Square neighborhood. The current trackless trolley routes are all former streetcar lines (the last four are not connected to the Tremont Street Subway). The MBTA and its predecessors once ran a large system of trackless trolleys that covered much of the lines north of Boston as well as separate groups in Dorchester and Jamaica Plain. The four current routes were created after much of the system was converted to diesel and exist, in part, because of the necessity to limit the number of diesel buses in the Harvard Tunnel. They are all stored overnight in the North Cambridge Carhouse, the northern terminus of the 77A. Trackless trolleys do not run on Saturday evenings and Sundays; instead diesel buses cover the routes.
In 2004, the MBTA began receiving a fleet of new trackless trolleys from Neoplan, to replace older Flyer trolleybuses dating to the 1970s. The newer vehicles meet Americans with Disabilities Act standards (see MBTA accessibility).
Additionally, the Silver Line Phase II uses dual-mode buses and until early 2006 also used some of the new Neoplan trackless trolleys pending the entry of the entire dual-mode fleet into service. As of July 2006, the Neoplan trackless trolleys have now all been transferred to the following routes, and most of the Flyer trolleybuses have been retired, with no more than a dozen being kept as spares.
The 71 Watertown Square - Harvard Station via Mt. Auburn St. begins at the Harvard Bus Tunnel lower level and leaves via the south exit onto Mount Auburn Street. It heads west into Watertown, ending at Watertown Square.
At the Harvard end, to turn around, the trackless trolley exits the tunnel and makes a hard left onto Massachusetts Avenue and a right on Garden Street, and then turns right on Waterhouse Street and right on Massachusetts Avenue to return to the tunnel. The Watertown end has a loop on private right-of-way for turning around and picking up/dropping off passengers.
September 4, 1958 was the last day of streetcar service on the 71, after which trackless trolleys have run.
The 72 Huron Ave. Harvard Station via Concord Ave. starts on the upper level and comes out the north end of the tunnel, using the path that the 71 uses to turn around. However, at the intersection of Garden and Waterhouse Streets, the 72 heads west on Garden Street, Concord Avenue and Huron Avenue and south on Aberdeen Avenue to end at Mount Auburn Street, intersecting the 71 and 73.
To turn around, the 72 leaves the south portal of the tunnel and turns left on Mount Auburn Street. It turns right on Eliot Street, right on Bennett Street and right on private right-of-way to go straight across Mount Auburn Street into the tunnel. At the west end, the 72 simply makes a U-turn across the wide median of Aberdeen Avenue. On Saturday evenings and Sundays, the 72 is combined with the 75 bus and the route extends to Belmont center.
Streetcars last ran on the 72 on April 1, 1938, and trackless trolleys have been running since then.
The 73 Waverley Sq. Harvard Station via Trapelo Road follows the same route as the 71 in Cambridge. It leaves Mt. Auburn St. to follow Belmont Street, which forms a border between Belmont and Watertown, then continues on Trapelo Road in Belmont to end at Waverley Square, with a loop at the Waverley commuter rail station on the Fitchburg Line. A short-turn loop exists at Benton Square, the intersection of Belmont Street and Trapelo Road. 
September 4, 1958 was the last day of streetcar service on the 73 (and 71 and 77A), after which trackless trolleys have run. As a streetcar line, the turnback loop was further west along Trapelo Road at Cushing Square. Streetcars first ran to Waverley Square on October 1, 1898.  The old streetcar tracks can be seen at Waverley Square.
The 77A is a short-turn trip of the 77 Arlington Heights - Harvard Station via Massachusetts Ave. bus. It simply exits the north end of the tunnel onto Massachusetts Avenue, which it uses to the loop at the North Cambridge Carhouse. At the Harvard end, it turns around in the same way as the 72. However, these loops are not normally made, as since January 2005, the only 77A trips are pull-ins and pull-outs to take 71 and 73 buses to or from the carhouse. They are listed in the 77 schedule.
September 4, 1958 was the last day of streetcar service on the 77A\, after which trackless trolleys have run. Until around 1967, the route was numbered 82.
- MBTA - Route 71 Watertown Square - Harvard Station via Mt. Auburn St.
- MBTA - Route 72 Huron Ave. - Harvard Station via Concord Ave.
- MBTA - Route 73 Waverley Sq. - Harvard Station via Trapelo Road
- MBTA - Route 77 Arlington Heights - Harvard Station via Massachusetts Ave.
- nycsubway.org - Boston Transit: Trolleybuses
- Tom's Trolleybus Pix Boston Page