Green Line "D" Branch

Commuter rail

Opening dates for the different sections are as follows:

The earliest part of the line to be built was the Brookline Branch of the Boston and Worcester Railroad, which opened in 1847. It stretched 1.55 miles (2.50 km) from the B&W main line south of Kenmore Square southwest to the current location of Brookline Village station. The B&W became part of the Boston and Albany Railroad in 1867.

Next came the Charles River Branch Railroad, opened Summer 1852 from the end of the Brookline Branch to Newton Upper Falls. The line was at first operated by the Boston and Worcester, but in 1856 it was merged into the New York and Boston Railroad (having been merged with the Charles River Railroad in 1853), a company intending to build a new route between Boston and New York City in competition with the Boston and New York Central Railroad. Both of these companies passed through several changes in name and ownership before they merged in 1868 to form the Boston, Hartford and Erie Railroad. The BH&E became the New York and New England Railroad in 1873 and the New England Railroad in 1895 before being leased by the New York, New Haven and Hartford Railroad in 1898.

In 1884, the Boston and Albany Railroad built a connecting line from Riverside on their main line southeast to what became Cook Street Junction on the NY&NE in Newton Highlands. The NY&NE had been sold to the B&A in 1882 north of the junction, giving the B&A full ownership of their Highland Branch. The B&A instituted loop service ("Newton Circuit"), going one way to Riverside on the main line and the other way on the Highland Branch; the NY&NE continued to use the branch as well.

In 1906 the New York, New Haven and Hartford Railroad built a new cutoff from Needham Junction east to their Dedham Branch at West Roxbury, and began routing NY&NE trains that way. However, in 1911, they too began running loop service on the "Needham Circuit", running one way on the old Boston and Providence Railroad to West Roxbury and the other way on the B&A Highland Branch.

NYNH&H service through Newton stopped in 1925 and the last B&A train ran over the Highland Branch on May 31, 1958.

Conversion to light rail

From mid-1958 to mid-1959, the Highland Branch from Riverside to Fenway was converted to light rail by Boston's Metropolitan Transit Authority. This was to be a low budget project and the light rail option was chosen over third rail rapid transit trains because the last two miles to downtown would be via an existing light rail subway. The primary $7M contract was let to the Perini Corporation with an additional $2M for work by the MTA, of which part was designated for added land purchases. With the Riverside terminal just off what is now Interstate 95 and a mile from today's I-90, the line would be a showpiece of park and ride mass transit from distant suburbs using an existing railroad right of way.

The major project parts included the following:

Light rail operation began on the Highland Branch on July 4, 1959, with single cars or 2 and 3 car trains, running from Riverside or Reservoir to Park St. Station downtown. It was intended to short turn every other rush hour train at Reservoir and berths at Park St. were marked "Riverside/Reservoir." But from the very start, ridership was heavy enough on the outer end of the line to require running nearly all trips to Riverside, the exceptions mainly at the very beginning and very end of the day. Scheduled service frequency ranged from 6 minutes during rush hours to 15 minutes late in the evening. The MTA chose to maintain at least a 10 to 15 minute headway throughout rather than short turn trains at Reservoir during off hours.

The Highland Branch was originally given route number 4. (Routes 1, 2, and 3 were today's Red Line, Orange Line, and Blue Line rapid transit, respectively.)

With few exceptions, on board fare collection has been used at the surface stations. Originally the fare was the flat 20 cent rapid transit fare. By 1961 a zone fare system, pay enter inbound and pay exit outbound, was instituted. Fare was 10 cents Riverside to Reservoir, 10 cents Reservoir to Fenway, and 20 cents Fenway to downtown (40 cents for the entire ride). From the mid 1970s to the mid 2000s the outbound ride from Fenway to Riverside was free to speed up alighting from the cars (and a somewhat higher fare charged for the inbound ride). Beginning in 1996, passengers prepaid their fares at the Riverside station, first during morning rush hour only and ca 2006 full-time. Also, after Red Sox games and during a few other heavily traveled times, passengers sometimes prepaid fares at other stations, notably Fenway.

In 1961, passenger boardings were reported at 30,000 per day.

No passenger connection has been provided between the Riverside light rail station and the Riverside station on the B&A main line, now the MBTA Commuter Rail Framingham/Worcester Line. B&A Service to the latter Riverside station ended in the 1970s although a pedestrian underpass and platform still exists, the underpass was closed in 2016 because it is in very poor condition. The nearest commuter rail station on the latter line is in the Newton village of Auburndale, about half a mile away. The tracks from the "D" Branch to the Boston and Albany main were severed and overgrown until, to facilitate the delivery of new light rail vehicles in the 1970s, they were rebuilt and have since been maintained, although they are not used for any regular service. Special commuter rail trains did run to South Station from a temporary platform near the Riverside light rail station from October 23–25, 1996 after heavy rain led to extensive flooding in the Boston area, closure of the Kenmore Square subway station and cutting off of the Riverside line from the downtown subway stations.

The MBTA takes over

By August 1964, when the MBTA took over, service on the Riverside Line was extended on all days but Sundays to Lechmere. Sunday service was extended on September 10, 1966.

In 1967, letter designations replaced the route numbers for the light rail lines and the 4 Riverside-Lechmere became the D Riverside.

Over the years, the following changes in eastern terminal have been made:

The MBTA's first Boeing light rail vehicles operated on the "D" Branch on December 30, 1976, and turned around at Park Street or Government Center due to the North Station loop catenary not yet upgraded for pantographs.

Use of PCC cars on the "D" line officially ended March 23, 1978, but later LRV shortages prompted the occasional return of PCC cars.

Track improvements

From the very start of light rail service, in 1959, there were complaints about rough riding followed by continual improvements to the track. While the ride was generally satisfactory at 30 MPH, many operators went faster. At least one news report, in response to riders encountering almost violent side-to-side swaying of the cars, mentioned a 35 MPH speed limit imposed by the MBTA management. (A PCC car can reach nearly 50 MPH on level track.) Also, continuously welded rail joints were gradually introduced.

When the first Boeing LRV was brought in for testing in the early 1970s, it became clear that the entire track would need to be rebuilt in order to support the greater weight of those cars and take advantage of their 50 MPH speed. Different techniques were used for maintaining service as each of three sections of the line were rebuilt.

The tracks were rehabilitated again in 2007. This project was undertaken because the newest LRV's, low floor handicapped accessible models from Breda, did not operate reliably over the tracks at the desired 40 to 50 mile per hour speeds. While the Riverside line generally received the newest cars first, it was the last to get the Breda cars due to the need to upgrade the tracks.

Traction electrical power

The Highland Branch, under the MTA and the MBTA, originally used trolley pole current collection and had simple suspension overhead with span wires. No changes were made in terms of current collection for the PCC cars.

The Boeing LRV's and their successors use pantograph current collection, except under unimproved overhead where only a few, equipped with trolley poles, operated for non-revenue purposes. Meanwhile, the PCC cars used trolley poles. The overhead for the entire Highland Branch was modified to handle both trolley poles and pantographs, with short runners installed at each switch frog to guide the pantographs past. The overall structure of the overhead remained unchanged for several more years.

At first, most of the overhead wire was not given a pronounced side to side stagger to spread out the wear on pantograph sliders. However inaccuracies in the original overhead construction perhaps together with a less noticeable side to side stagger added later improved pantograph operation while not detracting significantly from trolley pole operation.

By 1985, the MBTA was finally in a position to retire its PCCs from the Green Line as the issues plaguing the Boeings were resolved to a point where a majority of the cars operated reliably and the MBTA placed an order for additional light rail cars from Kinki Sharyo, which were delivered the following year. With the PCC cars retired, the Green Line operating fleet had become exclusively pantograph equipped, eliminating the need for the wire frogs that were used to guide the trolley poles' current collectors at switches. The overhead catenary received additional upgrades, the first of which used primarily span wire support from the existing line poles. The second upgrade used many more bracket arms. Due to the added weight of the new overhead construction, side guy wires were added to many existing line poles or a horizontal beam was installed across a pair of line poles.

Incidents and accidents

On May 28, 2008, just after 6pm, two trains collided between Woodland and Waban stations, behind 56 Dorset Road. The driver of the rear train, Terrese Edmonds, was trapped by the collision and died. The National Transportation Safety Board investigation concluded that the driver of the rearmost train probably had an episode of micro-sleep caused by sleep apnea.

About a year later, another crash, this one in the central subway, was blamed on an operator texting while driving.