As the Metropolitan Transportation Authority finalizes early construction plans for Phase 2 of the Second Avenue Subway, decisions being made now could determine whether a future westward extension under 125th Street is ever built.
That question has taken on new weight following Gov. Kathy Hochul’s Jan. 13 State of the State address, delivered as the administration began assembling its next multiyear capital and budget priorities.
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The governor proposed funding in the 2026 executive budget to advance design and preliminary engineering for extending the Second Avenue line west across 125th Street to Broadway—a policy direction that coincides with a narrowing decision window on Phase 2.
The timing matters: while Phase 2 has not yet entered tunneling, it has moved beyond planning. Utility relocation is underway, the main tunneling contract has been awarded, and terminal configuration and construction sequencing are being finalized ahead of heavy civil work scheduled to ramp up in 2026. Tunnel boring is not expected to begin until 2027.
Phase 2 will extend Q train service north from 96th Street to 125th Street and Lexington Avenue, adding stations at 106th, 116th and 125th streets. The project is scheduled to enter revenue service in September 2032, according to MTA project documents.
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MTA | 125th Street Subway Feasibility Study
Hochul said New Yorkers “deserve a world-class transit system,” framing the proposed design funding for a 125th Street extension as a way to build on existing investments while Phase 2 construction planning is underway. The administration has not committed capital funding for construction, but the proposal elevates the corridor from long-range planning into near-term design consideration.
Where Phase 2 Decisions Become Irreversible
Any westward extension along 125th Street would need to connect directly into the Phase 2 terminal while maintaining subway operating grades within tight tolerances.
The feasibility study identifies several high-stakes interfaces, including tail-track and crossover configuration at the 125th Street terminal, preservation of structural provisions for a future westward turnout, and retention of ancillary and staging parcels that could support tunnel launch, retrieval or station construction west of Lexington Avenue.
A map from the Metropolitan Transportation Authority’s December 2025 125th Street Subway Feasibility Study outlines the study area for a proposed westward extension from the Second Avenue Subway Phase 2 terminal, highlighting potential stations, major institutions and key Harlem destinations along 125th Street.
Map courtesy of the Metropolitan Transportation Authority
Those constraints are compounded by subsurface conditions. Geotechnical investigations found that much of 125th Street consists of mixed-face ground, with loose sand and gravel layered with clay and silt, while groundwater is typically encountered about 10 ft to 20 ft below grade.
Bedrock depth varies sharply, dropping from less than 100 ft below the surface east of St. Nicholas Avenue to more than 200 ft west of it near Broadway.
According to the MTA’s 125th Street Subway Feasibility Study, those mixed-face conditions, combined with shallow groundwater and extremely tight settlement tolerances beneath a dense urban corridor, make conventional drill-and-blast tunneling impractical for most of the alignment. The study instead advances pressurized, mixed-face tunnel boring machines as the baseline approach, citing their ability to maintain face pressure, control groundwater inflow and limit surface settlement above utilities, existing subway infrastructure and building foundations.
For station construction, the study anticipates that large underground caverns at Lenox Avenue, St. Nicholas Avenue and Broadway would be excavated in unstable, water-bearing soils, often above deep bedrock. It identifies extensive use of ground freezing, grouting and localized dewatering to stabilize soils, control inflows and manage settlement during excavation and lining.
To manage constructability risk across the corridor, the MTA evaluated multiple tunneling scenarios, including one- and two-TBM approaches launched either from the east near Second Avenue or from new staging sites west of Broadway.
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Several options would reuse TBMs deployed for Phase 2, potentially lowering capital costs but increasing schedule interdependence, while others would operate independently at the expense of additional staging, utility relocation and traffic-management complexity.
At a planning level, the feasibility study places a full three-station crosstown extension under 125th Street in the roughly $5 billion to $7 billion range, depending on alignment length, station configuration and construction approach.
The agency cautions that the estimate is intended for comparative analysis rather than budgeting and would be refined substantially during environmental review and preliminary engineering.
A longitudinal profile from the MTA’s December 2025 125th Street Subway Feasibility Study shows the proposed westward tunnel alignment beneath 125th Street and its required geometric tie-in to the Second Avenue Subway Phase 2 terminal, illustrating how grades, station depths and bedrock conditions constrain future extension options.
Sectional profile courtesy of the Metropolitan Transportation Authority
Planning-level analysis also found that the Broadway terminal option delivered the strongest cost-benefit performance due to higher ridership, greater travel-time savings and the largest reduction in vehicle miles traveled.
Ridership modeling projects approximately 163,900 average weekday trips by 2045 under the three-station scenario, substantially outperforming one- and two-station alternatives and maximizing connections with existing north-south subway lines.
MTA Chair and CEO Janno Lieber said Hochul “keeps stepping up to make sure the MTA can continue fixing, improving and expanding our amazing transit system,” signaling agency alignment with advancing design work while Phase 2 construction planning is underway.
The feasibility study stops short of recommending the extension move forward. No environmental review has been initiated, no funding has been identified and no delivery schedule has been established. Advancing the project would require formal environmental scoping, inclusion in a future MTA capital program and identification of dedicated funding sources.
Instead, the study’s central conclusion is conditional: that Phase 2 decisions being finalized now—well before tunnel boring begins—will materially influence whether a 125th Street crosstown subway remains feasible in the future.
The next inflection points will not come with a groundbreaking, but in how Phase 2 advances. Signals to watch include whether terminal geometry preserves a westward connection, whether ancillary and staging sites remain available, whether TBM demobilization plans allow for reuse, and whether the MTA initiates formal environmental scoping for a 125th Street alignment.
Absent those steps, the study suggests the window to integrate a future extension could narrow quickly as Phase 2 construction progresses.
