A large tunnel opening with construction equipment, rail tracks, and metal framing.

Scarborough Subway Extension & Yonge North Subway Extension Projects


Our Client’s Challenge

Metrolinx, the agency that manages and integrates road and public transport in the Greater Toronto and Hamilton Area, is undertaking one of Canada’s largest and most complex transportation initiatives to transform transit infrastructure in Ontario’s Golden Horseshoe region. The Scarborough Subway Extension (SSE) and Yonge North Subway Extension (YNSE) projects reflect the region’s need for modern, multi-modal transportation solutions for an area expected to grow from a population of 6.5 million to 10 million by 2045.

Our Solution

Gannett Fleming is delivering services as part of a joint venture partnership, OneT+, between Gannett Fleming Canada ULC and Arcadis Architects Canada Inc. OneT+ contracted with Infrastructure Ontario (IO) and Metrolinx to plan the SSE and YNSE projects, two of four new rapid transit subway lines planned in the Toronto metropolitan area. As technical advisor, OneT+ provides, directs, and coordinates a broad range of engineering, architectural, and technical advisory services to support overall planning, preparation, procurement, design, and construction.

Specific services provided include:

  • Project development, management, and controls.
  • Reference concept design for rail systems and station and tunnel infrastructure.
  • Cost estimating and construction scheduling.
  • Support for progressive design-build delivery model development and procurement.
  • Utility relocations and identification of property requirements.
  • Environmental planning and geotechnical and geo-environmental investigations.
  • Transit-oriented communities (TOC) integrated concept development.
  • Construction oversight, design compliance, quality management, safety oversight, reporting, and claims support.

SSE will replace the existing Scarborough Rapid Transit line and is a 7.8-kilometre rail extension of Line 2 from the existing terminal at Kennedy Station, including:

  • Three new stations.
  • Bus terminals.
  • Advance work packages.
  • Utility relocation.
  • Advance tunnel.
  • Emergency exit buildings.
  • Rail systems.
  • Vehicle integration.

YNSE, an extension of Line 1, features a similar scope of work to the SSE metro system, including planning for up to six new stations and a maintenance and storage facility. YNSE lies within the City of Toronto before crossing into the Region of York.

Both transit projects consist of multiple procurement packages and delivery models, categorized as advance works, advance tunnel(s), and station, rail, and systems (SRS). The delivery model for the tunnel contracts is design-build finance, while the SRS contracts employ a progressive design-build approach.

Key Features

Scarborough Subway Extension

  • 8-kilometre extension of Line 2 (Bloor-Danforth) subway.
  • Single-bore, 10.7-metre-diameter single subway tunnel, the first of its kind in Toronto.
  • Three new stations: Lawrence East Station, Scarborough Centre Station, and a terminal station at Sheppard East Station.
  • Emergency exit buildings, traction power substations, and modifications at Kennedy Station.
  • Transit connections to Line 2, Line 5 – Eglinton Crosstown Light Rail Transit (LRT), and GO Train service (Stouffville Line).
  • Planning for future rail service connections to Line 4 (Sheppard Subway Extension) and potential Eglinton East LRT and Durham-Scarborough bus rapid transit (BRT) service.
  • Integration of TOC at each station, including the expanding Scarborough Centre.

Yonge North Subway Extension

  • 7.4-kilometre extension of Line 1 (Yonge-University-Spadina) subway north from Finch Station to Richmond Hill.
  • Train storage and light maintenance facility.
  • Bus terminals.
  • Commuter parking facilities.
  • Transit connections to VIVA BRT and GO Train service (Richmond Hill Line).
  • Integration of TOC, including the Richmond Hill/Langstaff Gateway Urban Growth Centre.


  • Improves rapid transit transportation services for area residents integrated with bus, light rail systems, cycling, and passenger drop-off/pick-up facilities.
  • Reduces daily travel times for commuters.
  • Integrates transit and high-density, mixed-use development for sustainable growth.
  • Economic and community growth along the future transit line and job creation opportunities.
  • Reduces traffic congestion, greenhouse gases, and fuel consumption by providing multi-modal transport solutions.

Awards & Recognition

  • Awards. This web part is hidden.


Infrastructure Ontario and Metrolinx


Toronto, Ontario


Engineering and Technical Advisory Services

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