Indigo Line

The Indigo Line was a proposed rapid transit service of the Massachusetts Bay Transportation Authority that would have incorporated parts of the former Grand Junction Railroad, the Seaport District's Track 61, a spur to Riverside station and other MBTA Commuter Rail lines.

The Indigo Line project was officially proposed in 2014 and was canceled in 2016.

History
Conversion of underutilized rail infrastructure within the Greater Boston area into regional rail or semi-metro services has been discussed for several decades, mostly in relation to the Fairmount Line. The term "Indigo Line" dates back to the creation of the Fairmount Indigo Planning Initiative in 2012; this study was facilitated by the Boston Redevelopment Authority (now the Boston Planning and Development Agency) which recommended transforming the Fairmount Line into a hybrid rail line (similar to New Jersey Transit's River Line). The hybrid approach was intended to be a low cost alternative to implementing high-frequency services on existing right-of-ways through the use of small lightweight rolling stock.

2014 proposal
The Indigo Line project was formally proposed as a MBTA capital project in 2014 with the release of its annual five-year capital plan; the proposal was further outlined within the "MBTA Vision for 2024" proposal the same year.

As proposed within the Vision for 2024 plan, the Indigo Line would have operated diesel multiple units for its rolling stock and would be fully operational in that year. The proposed 2014 state budget included $240 million to purchase DMU railcars; the state issued a request for proposals to purchase 30 trainsets with deliveries starting in 2018. An order of Nippon Sharyo DMUs for Sonoma–Marin Area Rail Transit in 2014 included an option for 18 cars to be provided to the MBTA for the Indigo Line service. Additionally, the plan called for the installation of a pre-pay fare system on Indigo Line routes with fixed fare pricing, similar to the MBTA subway.

Routes considered
The MBTA Vision for 2024 map proposed six possible lines to be upgraded for Indigo Line DMU service:


 * The current Fairmount Line
 * South Station to Riverside via the Framingham/Worcester Line and an old right of way from that line to Riverside currently used for trolley operator training
 * Back Bay to the Boston Convention and Exhibition Center using Track 61
 * North Station to the planned West Station using the Grand Junction Railroad, with a new stop in Cambridge
 * North Station to Anderson RTC on the Lowell Line
 * North Station to Lynn on the Newburyport/Rockport Line

Project cancelation
Funding for the Indigo Line project would be blocked by the Baker administration in 2016. The abandonment of the project was attributed to costs associated with acquiring specialized rolling stock along with general skepticism towards the practicality of the overall service. Opponents to the service cited the low ridership of the Fairmount Line (weekday ridership was 2,652 in 2018), as well as questioned the operational logistics of the proposed routes (mainly pertaining to how the Track 61 line would have bypassed South Station).

Partial implementation
The Fairmount Line Improvement Project adopted by the MBTA is based on preliminary Indigo Line plans; however, in its initial proposal the MBTA did not plan to increase service frequency to match rapid transit lines, nor to install pre-pay fare systems. The infill stations proposed by the initiative have been built; however, the line still uses conventional commuter rail equipment.

Additional proposals
The Indigo Line terminology was revived in 2023 within both Senate and House versions of a bill that would mandate the conversion of the MBTA's Fairmount Line to fully electrified operations by 2029 in order to effectively integrate the line with the MBTA’s rapid transit network under the Indigo Line banner. The 2023 legislation diverges from a previous MBTA proposal from 2022 that suggested the procurement of battery multiple units for the Fairmount Line as opposed to full electrification. The legislation was included in a Joint Committee on Transportation hearing on May 8, 2023, which has since been referred to the House Ways and Means Committee.

On March 16, 2024, MBTA Commuter Rail operator Keolis solicited a proposal that outlined the implementation of BEMU services on the Fairmount Line by FY 2027 as leverage for contract renewal; however, the MBTA has not reciprocated this motion as a formal project.

Despite renewed legislative support, the Indigo Line has not been formally proposed as a MBTA project and is not in active development.