NORTHFIELDS & COCKFOSTERS DEPOT

DPH delivered a coordinated programme of electrical and depot infrastructure upgrade works across Cockfosters Depot and Northfields Depot for Transport for London, supporting key enabling activities for the wider Piccadilly Line Upgrade and the introduction of the new, longer trains. Delivered within live, operational depot environments, the programme required controlled sequencing, possession planning and close stakeholder coordination to maintain depot operations while progressing safety-critical upgrades to traction power, isolation systems and depot access arrangements.

Across Northfields Depot, DPH delivered a broad scope of traction power and enabling works including the installation of Track Isolator Switch (TIS) bases, substation interfaces and associated cable route works. This included TIS Base 1, Base 2, Base 3 and Base 4, with the installation of TIS switches onto bases using RRV under possession, alongside associated contactor panel enabling works. DPH also completed substation cable penetrations with full fire stopping, installed steelwork to support new cable routes, and carried out phased cable pulling works along the traction supply route installing over 600m of 935mm² DC traction supply cabling. In parallel, DPH delivered depot operational and compliance works including platform earthing, the installation of cross-track walkway provisions, and lux level testing to verify lighting performance in operational areas. Driver Access Platform (DAP) alterations were delivered during planned possession windows, resulting in completed modifications and improved safe access across depot areas. DPH also completed supporting works such as welfare cabin electrical and mechanical works, strip-out and tag & trace surveys within back-of-house office areas and the relocation of equipment including antenna devices on depot roads.

At Cockfosters Depot, DPH delivered major enabling works supporting upgraded depot isolation and traction power routing. This included the installation of multiple TIS bases (Bases 1–5), associated lifting and placement activities, and the delivery of DAPS works including DAPS 1 & 2 with civils bases and relocation, plus DAPS 3 civils works and associated modifications. DPH also completed extensive containment renewal works supporting cable route upgrades, including the removal of existing troughing and installation of new replacement routes, concrete repairs, and cable management adjustments within depot environments. A significant element of the Cockfosters scope included traction cable installation works, including a DC cable pull of 12 runs of 935mm² cable, supporting upgraded traction supply distribution. Following completion of the revised cable route, DPH also carried out follow-on activities including fibre pulls, CMS replacement works and cable re-routing within equipment rooms to suit the updated containment arrangement.

Together, the works at Cockfosters and Northfields demonstrate DPH’s capability to deliver integrated depot upgrade programmes combining traction power, civils and electrical infrastructure, containment renewal and operational access improvements within live TfL environments. Through disciplined planning, flexible delivery under short possession windows and strong coordination with stakeholders, DPH successfully delivered the programme to a high standard of safety, quality and compliance, supporting the readiness of both depots for the continued rollout of the Piccadilly Line Upgrade programme.