Dolphin Junction upgrade
We’re improving an important junction in Berkshire for better passenger journeys
Over an eight-month period we are replacing and enhancing the eastern side of Dolphin Junction, between Slough and Langley stations, to reduce rail traffic congestion and improve reliability for journeys through the Thames Valley into London. It follows an upgrade on the western side of the junction during Christmas 2025.
Work has begun to install new overhead electrification equipment. With a new track layout being installed, the position of existing masts and gantries that carry the overhead power lines needs to change, along with some of the signalling equipment. Points operating equipment is being updated to state of the art technology.
The bulk of the track work takes place during the autumn and over the Christmas to New Year period. Once complete at the start of January 2027, the new track layout will allow trains to enter the junction, change lines and exit at greater speed. This will reduce congestion as trains passing through will no longer be held up waiting for others to switch between main and relief lines and get clear of the junction.
Project in numbers
- £27.8m invested in renewing and enhancing Dolphin Junction.
- Over 400 passenger trains pass through Dolphin Junction every day
- 123 million tonnes of freight are carried over the junction each year
- 88 pre-constructed track panels will be fitted together like a huge jigsaw, making up the new track layout on the eastern side of the junction.
- Nine new structures for overhead power lines are being installed including four gantries.
- One kilometre of new wire for overhead power lines is being installed onto the new gantries and masts alongside the existing wire through the junction.
- State of the art points operating equipment is being installed and two signals are being relocated, along with lineside location cabinets and other signalling components.
Project timeline
June / July 2026: Piling foundations and installing new masts and components for updated overhead electrification equipment. This work runs into August.
August / September 2026: Vegetation management, lineside signalling equipment installation, delivery of rail and specialist pre-constructed track panels.
October / November 2026: Remove scrap and redundant electrification equipment, delivery of pre-constructed track panels. Installation of new track (during the 28/29 November weekend closure of the railway).
December 2026 / January 2027: Ongoing track renewal work and preparation for installation of the new points during the 10-day closure of the railway over the Christmas and New Year period.
Travel information
Our work at Dolphin Junction near Slough will affect train services for London Paddington:
- 28/29 November 2026
- 27 December 2026 – 3 January 2027 (following the usual Christmas shut down on 25 and 26 December 2026)
Alternative travel arrangements, including diversions, are being agreed. Once details are confirmed information will be posted here.