1st St. stop configuration

1st St. stop configuration

The main transport objectives of the project are to:

  • Relieve crowding in the downtown core of the transit system
  • Decrease auto use
  • Link major employment centers, including the Longwood Medical Area and Kendall Square, which contain the largest number of jobs outside of Downtown and the Back Bay
  • Increase transit service for underserved communities
  • Foster opportunities for development along the ring, especially in areas with strong potential for redevelopment of industrial land

This page highlights ways to achieve these objectives, the transportation context of the corridor, and our analysis of demand. For the 8 mile (12 km) long first phase of the corridor, we expect medium-term demand in the range of 30,000 to 50,000 average weekday boardings.

Context and Existing Travel Patterns

The Longwood Medical Area and Kendall Square contain the largest number of jobs outside of the Boston core. Based on the radial layout of the existing transit network, many trips destined for these areas involve transfers in the downtown core of the heavy rail system, which is experiencing increasing congestion. The Diamond Ring will help alleviate this crowding by improving connections to these two employment centers, while also increasing transit access for surrounding residential communities.

Residential Density

Residential Density

Employment Density

Employment Density

The Boston region is subject to significant traffic congestion, especially in the southern section of the proposed corridor.

Estimated Traffic Congestion

Estimated Traffic Congestion

Selected Alignment

The alignment consists of a mix of:

  • Bus ways: Dedicated streets for use only by transit buses, emergency vehicles, pedestrians and cyclists.
  • Bus lanes: dedicated Lanes for bus use on existing roadways
  • Mixed traffic: Buses and regular traffic share the roadway.
  • Bus/Train shared ROW [Cambridge Section only]

The suggested alignments along existing roadways were chosen after study by each segment team regarding feasibility, efficiency, connectivity and congestion. Some sections of the alignment, especially in the southern half, appear to suffer from high levels of congestion but were still determined to be the best location for the alignment. These factors are discussed in the segment detail pages.

Diamond Ring Alignment

Diamond Ring Alignment


From north to south, DR1 service will make the following stops:

  1. Assembly Square (Connection with Orange Line)
  2. Sullivan Square (Connection with Orange Line)
  3. Inner Belt / Brickbottom
  4. Lechmere (Connection with Green Line D and E branches)
  5. First St / Galleria
  6. Binney St
  7. Kendall Square (Connection with Red Line)
  8. Massachusetts Ave / MIT
  9. Cambridgeport
  10. BU East (Connection with Green Line B branch)
  11. BU West (Connection with Green Line B branch)
  12. Yawkey (Connection with Framingham/Worcester Commuter Rail Line and Green Line C and D branches)
  13. Longwood Medical Area
  14. Museum of Fine Arts (Connection with Green Line E branch)
  15. Ruggles (Connection with Orange Line Franklin/Needham/Providence Commuter Rail Lines)
  16. Dudley Station (Connection with Silver Line)
  17. Dudley Common

Modular station units with real-time information and fare prepayment infrastructure will be deployed according to station demand.


Similar to the DEIR proposal for the project, the first phase of the project, DR1, will provide 3-minute peak headways, requiring 37 additional buses. Existing CT2 service will be upgraded with improved stops and rebranded as the DR2 to complement DR1 service. Given the wide spacing between stops in the basic service pattern, express services are not proposed in the initial phase, though high demand may eventually warrant express service.

Demand – Shift from Existing Transit Trips

Based on the Massachusetts Travel Survey (MTS), which was organized by trip stages, a tour-based database was constructed in order to quantify the trips that would benefit from the Diamond Ring (potential users) based on their reported origin, destination and mode.Even though for transit ridership we usually care about trip stages, the idea of going from stages to tours is to see who the project benefits more broadly. Doing a tour-based analysis that includes the location of transfers allows us to get (1) internal transit trip stages within the study area that could be done with the new system, and (2) trips with transfers in the downtown core for which the new system would be a better alternative. Most of these second type of trips currently do not have a stage in the study area, and therefore would not be identified in a trip stage analysis. Avoiding these transfers is also one of the main objectives of the project.For the analysis, 4 macro areas were established:

Macro-zones for Demand Analysis

Macro-zones for Demand Analysis

The study area is a buffer of 500m around the proposed semi-circumferential Diamond Ring alignment.

The Inner City (light red) is the downtown area, which is connected to the Study Area (yellow) through the existing radial transit network.

The outer city area (light green) is separated from the downtown by our study area (yellow). So trips with origins in this area, destination in the study area, and transfers in the downtown area, could be “intercepted” by the Diamond Ring, eliminating the need to transfer downtown.

Unlike the outer city, trips coming in transit from the “External” (gray), with destination in the study area will necessarily have to go through downtown. That is, they don’t cross the study area and then return back to it, as trips from the outer city do. Therefore, the Diamond Ring will be no use in preventing them from transferring in downtown. The limits of these areas are based on the transit network in relation to the study area.

The locations of the trip’s origins, destination and transfers were coded using these macro areas. Additionally, a General Mode was established for every trip as follows:
• Non Motorized: trips done by walking or bicycle alone
• Transit: trips that use bus, subway or commuter rail in at leas one stage of the trip
• Private vehicle: trips that only use private car or motorcycle, or private car or motorcycle plus walking
• Taxi: trips that only use taxi, or taxi plus walking
• Other: trips that only use other modes

With these location and mode categories, the following potential Diamond Ring ridership shifted from existing transit trips was calculated:

Primary trip type Code Number of Expanded Trips from MTS
O in study area, D in study area Internal 9,400
O in outer city, D in study area, transfer in inner city External 1 13,800
O in outer city, D in study area, transfer in corridor External 2 5,300
O in inner city or external area, D in study area, transfer in study area External 3 2,200
O in study area, D outside study area, transfer in study area External 4 8,900
Total shift from existing transit trips 39,600

Demand – Shift from Auto and Taxi Trips

Private vehicle and taxi trips from the MTS were analyzed in a similar way to estimate mode shift.

Additional demand from mode shift Number of Expanded Trips from MTS
Internal trips
Private Veh, assuming a 10% capture Private 3,950
Taxi, assuming a 15% capture Taxi 50
From and to external areas
Private Veh, assuming a 10% capture Private 150
Taxi, assuming a 15% capture Taxi 50
Total from mode shift 4,200
Predicted average weekday boardings, first year of operation 43,800

An independent 4-step model developed in Cube predicted 55,000 average daily boardings in the DR1 corridor, with 7,600 of these boardings occurring during the morning peak.

Demand – Long Term Development

Longer term transportation network changes and real estate development are both expected to add to ridership. We estimate that the Green Line Extension to Somerville and Medford will add 2,500 additional trips to the Diamond Ring, and that new residential and commercial development along the corridor will add close to 20,000 additional trips in the coming decade.Compounded by increasing urban density and decreasing auto ownership, we expect that corridor ridership could surpass 80,000 average daily boardings in after two decades of operation.

Electric Vehicles

Electric vehicles face some challenges, one of which is autonomy. Despite battery technology advancements in the last few years, autonomy is still the key barrier preventing the adoption of electric vehicles in general, especially because of their weight. However, predictable routes and accurate schedules for the Diamond Ring would help to alleviate this problem, since charging episodes could be planned ahead of time.To evaluate the feasibility of using electric buses in the corridor, a simulation platform for an electric bus powertrain was implemented in Simulink and the open-source traffic simulator SUMO. Both simulators are integrated via a high-level software architecture approach, allowing the bus simulated in Simulink to perform a route designed on SUMO that later gives feedback to Simulink in order to perform the calculations. The outcome from this platform is the energy consumption for a certain route, average speed, acceleration rates among others.For the simulation of the Diamond Ring, the following parameters were considered:
• Acceleration rate: 0.6 m/s2
• Deceleration rate: 0.9 m/s2
• Maximum allowed speed: 60 km/h
• Time at bus stops: 20 s

The alignment and stop locations for the Diamond Ring were modeled in SUMO. Random traffic was generated, with probabilities assigned according to the number of lanes and the length of the street.Based on this preliminary analysis, electric buses appear to be a feasible option for the proposed corridor. The power required for a one-way trip was estimated to be 25 kW, which is within the capabilities of existing battery systems.

Some bus stops could be equipped with fast-charging stations that could recharge a bus in 30 minutes in the event of emergencies or unplanned service interruptions. However, the corridor discussed in this report includes four segments with a small combined length of less than nine miles. For these types of distances it would be possible to conduct all charging episodes at the bus depot during the night and avoid recharging sessions during the day.

Ongoing work comprises importing a traffic OD matrix to this system to represent actual traffic more accurately, as well as simulating boardings and alightings. Additional corridors, including the SL6, were also modeled and found to be feasible candidates for electric vehicle implementation.

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