The Red Line is a rapid transit

Rapid transit

A rapid transit, underground, subway, elevated railway, metro or metropolitan railway system is an electric passenger railway in an urban area with a high capacity and frequency, and grade separation from other traffic. Rapid transit systems are typically located either in underground tunnels or on...

 line operated by the MBTA

Massachusetts Bay Transportation Authority

The Massachusetts Bay Transportation Authority, often referred to as the MBTA or simply The T, is the public operator of most bus, subway, commuter rail and ferry systems in the greater Boston, Massachusetts, area. Officially a "body politic and corporate, and a political subdivision" of the...

 running roughly north-south through Boston, Massachusetts into neighboring communities. The line begins west of Boston, in Cambridge, Massachusetts

Cambridge, Massachusetts

Cambridge is a city in Middlesex County, Massachusetts, United States, in the Greater Boston area. It was named in honor of the University of Cambridge in England, an important center of the Puritan theology embraced by the town's founders. Cambridge is home to two of the world's most prominent...

 at Alewife station

Alewife (MBTA station)

Alewife, located at the intersection of Alewife Brook Parkway and Cambridgepark West in Cambridge, Massachusetts, is a local intermodal transportation hub. It is the northern terminus of the MBTA's Red Line, and a bus terminal for several local routes and one intercity route. It opened in 1985.The...

, near the intersection of Alewife Brook Parkway

Alewife Brook Parkway

Alewife Brook Parkway is a short parkway in Cambridge and Somerville, Massachusetts. It is listed on the National Register of Historic Places. It begins at Fresh Pond in Cambridge , and heads north on the east bank of Alewife Brook, crossing into West Somerville and ending at the Mystic River on...

 and Route 2. The line passes through downtown Boston, with transfers to the Green Line

Green Line (MBTA)

The Green Line is a streetcar system run by the Massachusetts Bay Transportation Authority in the Boston, Massachusetts area of the United States. It is the oldest line of Boston's subway, which is known locally as the 'T'. The Green Line runs underground downtown and on the surface in outlying...

 at Park Street station

Park Street (MBTA station)

Park Street is a rapid transit and light rail station of the MBTA subway system in Downtown Boston. One of the four subway hub stations, Park Street is a transfer point between the Green and Red Lines. Park Street is the fourth-busiest station in the MBTA network, with an average of 19,836 entries...

, the Orange Line

Orange Line (MBTA)

The Orange Line is one of the four subway lines of the Massachusetts Bay Transportation Authority. It extends from Forest Hills in Jamaica Plain, Boston in the south to Oak Grove in Malden, Massachusetts in the north. It meets the Red Line at Downtown Crossing, the Blue Line at State, and the Green...

 at Downtown Crossing

Downtown Crossing (MBTA station)

Downtown Crossing Station of the MBTA, located at the corner of Washington Street and Summer Street and the corner of Chauncey Street and Summer Street in Boston, is the main transfer point between the Orange Line and the Red Line....

, and the Silver Line

Silver Line (MBTA)

The Silver Line is the only bus rapid transit line currently operated by the Massachusetts Bay Transportation Authority . It operates in two sections; the first runs from Dudley Square in Roxbury to downtown Boston, Massachusetts and South Station, mostly via Washington Street, with buses...

 at South Station

South Station (MBTA subway station)

South Station also known as South Station Under is a station on the MBTA Red Line subway and Silver Line bus rapid transit located at Summer Street and Atlantic Avenue in Boston. It is a part of the South Station complex, the second busiest transportation center in New England...

. South of downtown, the line splits at JFK/UMass station

JFK/UMass (MBTA station)

JFK/UMass Station is located at the intersection of Columbia Road and Morrissey Boulevard, in the Dorchester neighborhood of Boston, Massachusetts.Its facilities include:*a platform on the Boston subway's Red Line for the Ashmont Branch...

, where one branch provides service to Braintree station

Braintree (MBTA station)

Braintree, located at Ivory and Union Streets in Braintree, Massachusetts, is the southernmost station on the Massachusetts Bay Transportation Authority's Red Line. It also is a stop on the MBTA Commuter Rail Old Colony Lines...

 and the other to Ashmont station

Ashmont (MBTA station)

Ashmont is located on the Red Line in Dorchester, Massachusetts. It opened on September 1, 1928, and is the subway terminal for the Red Line's Dorchester Branch. Ashmont is also the terminus of the light rail Ashmont–Mattapan High Speed Line, which loops around on an elevated viaduct...

.