🛤️ SRSA: South Rail Systems Alliance

📐 Programme scope

SRSA is one of three parallel Rail Systems Alliances Network Rail runs as part of a wider ~£5bn track and rail systems renewals programme. It was formed in 2019 as a 10-year framework (2019 to 2029), running a target-cost, pain/gain alliance commercial model under a shared alliance charter, spanning CP6 into CP7.

Partners: Colas Rail (constructor/installer), Network Rail (client and alliance partner), AECOM (designer). No fourth named partner found in any source.

Its HS2-relevant scope centres on Old Oak Common: decommissioning the former Heathrow Express depot (Sept 2019 to Nov 2021, ~£2.5m value-engineering savings), and ongoing rail systems infrastructure works (OLE, drainage, S&C, signalling) for the new 8-platform conventional GWML/Elizabeth line/Heathrow Express station, most recently a five-day multidisciplinary blockade over Christmas 2024 under Network Rail's "On Network Works" programme.

🗺️ Where it sits in HS2's wider structure

SRSA is a Network Rail-let alliance delivering enabling and rail systems work that interfaces with HS2 Ltd's build at Old Oak Common, not an HS2 Ltd main-works contractor itself. HS2 Ltd's own "Railway Systems" contractor grouping for the underground HS2 platforms/tunnel corridor (Old Oak Common to Chiltern tunnel north portal) is a separate structure: Ferrovial BAM, Costain, Siemens Mobility, and Colas Rail Limited (for the standalone OCS contract above). SRSA itself does not appear as a named contractor on HS2.org.uk or networkrail.co.uk's own HS2 station pages, only on Colas Rail's own press site and trade press republishing it, plus (per a search snippet) Network Rail's June 2025 Key Delivery Partners map (PDF, not directly text-verified).

📅 Current 2026 status

Active. Recent confirmed activity: Poplar Rail Lines electrification at Acton (Anglia side energised Nov 2025, Western side power upgrade 27 Dec 2025, full operational capability targeted Easter 2026); Westbury works wrapped up (2025); Cambridge South infrastructure upgrades completed (reported May 2025).

👥 Key people

🤝 Contractors & JV partners

• Colas Rail: constructor/installer, rail systems delivery partner
• Network Rail: client and alliance partner, asset owner
• AECOM: designer

SRSA is one of three parallel Rail Systems Alliances Network Rail runs; incumbent alliance partners named in 2026 CP8/CP9 re-procurement coverage across all three alliances include Babcock Rail, Balfour Beatty and Colas Rail.

📋 Delivery / access-planning model & terminology

SRSA and Colas Rail materials use standard Network Rail industry terminology, not bespoke alliance jargon. "Blockade" is the term used repeatedly in their own press releases (e.g. "five-day multidisciplinary blockade" at Old Oak Common Christmas 2024, "10-day project" blockade at Cambridge South, "16-day possession" at Severn Tunnel). "Possession" is used generically. Network Rail's own "On Network Works" programme name is used as the umbrella for the OOC Christmas 2024 blockade.

📝 Running reference notes

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🔗 Sources