Ashmont–Mattapan High Speed Line

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PCC inbound at Milton.jpg
An inbound PCC car at Milton
Type Light rail
Locale Boston, Massachusetts (Dorchester to Mattapan) via Milton, Massachusetts
Termini Ashmont
Stations 8
Services 1
Daily ridership 4,637[1]
Opened August 26, 1929 (Ashmont to Milton)
December 21, 1929 (Milton to Mattapan)[2]
Owner MBTA
Operator(s) MBTA
Character Private right-of-way (largely grade-separated)
Rolling stock PCC streetcar
Line length 2.54 miles (4.09 km)
Track gauge 4 ft 8 12 in (1,435 mm)
Minimum radius 43 ft (13.106 m)[3]
Electrification 600V Overhead lines
Route map
Red Line to Alewife
0 mi (0 km) Ashmont Red Line 
0.35 mi (0.56 km) Cedar Grove
0.95 mi (1.53 km) Butler
Neponset River
1.25 mi (2.01 km) Milton
Central Ave.
1.54 mi (2.48 km) Central Avenue
1.98 mi (3.19 km) Valley Road
Capen St.
2.31 mi (3.72 km) Capen Street
2.54 mi (4.09 km) Mattapan
Mattapan Yard/Loop

Geographic map of the line

The Ashmont–Mattapan High Speed Line, also known as the "M-Line", is a partially grade-separated light rail line which forms part of the MBTA's Red Line rapid transit line. The line, which runs through Boston and Milton, Massachusetts, opened on August 26, 1929 as a conversion of a former commuter rail line and exclusively uses historic PCC streetcars for rolling stock. Passengers must transfer at Ashmont to access the rest of the Red Line, which uses heavy rail metro rolling stock.

The term "high speed line" is a historic vestigial designation, distinguishing the exclusive and largely grade-separated right-of-way at a time when most trolleys ran down streets shared with automobiles. The 2.6 miles (4.2 km) route is used only by streetcars and has just two public grade crossings. All stations have low platforms, but all except Valley Road have been retrofitted with wheelchair lifts or wooden ramps for handicapped accessibility.

History and route[edit]

Most of the right-of-way is grade-separated
Grade crossing at Central Ave station

The Ashmont–Mattapan Line follows the right-of-way of the Dorchester and Milton Branch Railroad, opened December 1847. It became part of the Old Colony Railroad and then the New York, New Haven and Hartford Railroad after 1893. Steam trains were discontinued in 1927 and the line was closed for two years while it was modified for streetcars. There was a debate at that time whether or not to continue subway trains from Boston to Ashmont onwards to Mattapan, but the cost of full-scale subway service was apparently too high for the BERy which then operated it. The line opened from Ashmont to Milton on August 26, 1929, and from Milton to Mattapan on December 21, 1929.[2]

The portion of the line from Ashmont to Cedar Grove and through a cemetery follows the path of the original Shawmut Branch of the Old Colony Railroad, which opened in 1872. The cemetery is where the Shawmut Branch intersects with the original Dorchester and Milton Branch. The right-of-way is owned by the MBTA and has only two at-grade crossings on its 2.6 miles (4.2 km) route.

The line's longest shutdown started June 24, 2006 while the Ashmont and Mattapan stations were renovated. Service was restored on December 22, 2007.[4] Several of the stations have been renovated for better accessibility and modernization; all stations are now wheelchair-accessible except Valley Road, which is down a grade from the nearest road with no room for a ramp.


Using funding from the American Recovery and Reinvestment Act of 2009, the MBTA has been conducting a pilot test of technology similar to a collision avoidance system in an automobile, using radar and increasingly fast beeping to warn train operators of obstacles ahead. Like positive train control, it would stop the train if the driver did not take action to avoid an impending collision.[5] If successful, the system would be considered for deployment on the Green Line, where multiple collisions have occurred in recent years.

On November 26, 2014, an out-of-service car collided with an in-service car near Cedar Grove. Seven people were injured.[6]

Rolling stock[edit]

The rolling stock consists of rebuilt PCC streetcars, like those that formerly ran on the Green Line. Unlike most heritage streetcar operations, the Ashmont-Mattapan Line is an integral part of the rapid transit system rather than a tourist attraction. The historic rolling stock is retained largely because the line, built for 1920s streetcars, would have to be substantially rebuilt to accommodate the heavier modern cars used on the Green Line.

The current set of PCC cars have been in continuous revenue service since the late 1940s except for maintenance and rebuild programs. Around 2000, the PCC rolling stock was repainted in Traction Orange and Cream, with a Maroon belt and Black trim, similar to the paint scheme the cars were originally delivered in between 1944 and 1946. The cars also carry a "special" MBTA logo, reminiscent of the old Metropolitan Transit Authority Map Logo found on the cars between 1948 and 1955.


To clear the line of snow, the MBTA maintains a jet engine powered snowblower, officially the Portec RMC Hurricane Jet Snow Blower, model RP-3, dubbed "Snowzilla" by MBTA spokesman Joe Pesaturo. Snowzilla weighs 26,000 pounds, measures 8 by 12 by 27 feet, and is powered by a Westinghouse J34 turbojet engine. It uses approximately 500 gallons of jet fuel per line clearing run. Other T lines simply run regular trains to clear the tracks of snow, but the older cars on this line would short out if used for that purpose.[7]




  1. ^ "Ridership and Service Statistics" (PDF) (14 ed.). Massachusetts Bay Transportation Authority. 2014. Retrieved 26 November 2014. 
  2. ^ a b Belcher, Jonathan (22 March 2014). "Changes to Transit Service in the MBTA district" (PDF). NETransit. Retrieved 26 November 2014. 
  3. ^ Transportation Research Board Executive Committee 1995 (1995). "Applicability of Low-Floor Light Rail Vehicles in North America" (PDF). US Federal Transit Admininstration. Retrieved 11 August 2011. 
  4. ^ "Mattapan Trolley to Re - Open". Massachusetts Bay Transportation Authority. 20 December 2007. Archived from the original on 23 December 2007. Retrieved 24 December 2007. 
  5. ^ Associated Press (2 July 2009). "MBTA testing trolley collision-avoidance system". Boston Herald. Retrieved 11 August 2011. 
  6. ^ "Two MBTA Trolleys Collide, 7 People Reported Hurt". Boston Globe. 26 November 2014. Retrieved 26 November 2014. 
  7. ^ Eric Moskowitz (January 23, 2011). "Snowzilla vs. winter’s fury". Retrieved February 20, 2015. 

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