The road bridge carrying the A1 Holloway Road over the railway line at Upper Holloway station has been replaced. The £25m rebuild project is part of a Transport for London (TfL) scheme to improve London's roads and public spaces. It has been challenging and complex from feasibility to implementation.
Holloway Road Bridge is a single span bridge near Archway in the London Borough of Islington. It is one of four road-over-rail bridge replacement projects included in Work Package 1 of STIP (Structures and Tunnels Investment Portfolio). The three other projects are: Highbury Corner Bridge on the A1, the A127 Ardleigh Green Railway Bridge and the A406 Power Road Railway Bridge.
Overview of a challenging and complex scheme
The Holloway Road Bridge scheme involved advanced works to install a new service bridge overnight, and coincided with Network Rail’s electrification of the railway underneath, which added significant complications for the bridge solution.
The design of both the service bridge and the replacement highway bridge required complex 4D building information modelling. It considered features required for each of the utility services including chambers, bends and thrust blocks, as well as the future maintenance requirements of the numerous statutory undertakers (including local and regional gas, water, electricity, telecoms and cable).
Replacement of the main bridge structure was planned to take place over a four day closure of the railway, which coincided with possession for the on-going electrification works.
Replacement was the preferred option
The original bridge had reached the end of its operational life and was beyond simple repair. It carries two traffic lanes and two bus lanes over rail lines. Without replacement, the safe operation of the bridge would require restricting the weight of vehicles using the bridge and closing lanes for maintenance of utility pipes or cables buried in the carriageway. Replacement with a new structure was the preferred option to avoid long-term disruption to traffic and rail operations.
The replacement bridge structure has an expected lifespan of 120 years.
Three key phases of the work
- Service bridge installation. A new service bridge, which also serves as a station footbridge at Upper Holloway, was lifted into place by contractors Hochtief (UK) using one 300 ton crane in June 2016.It will carry the utilities (gas, water, electricity and telecommunications), which were previously buried in the carriageway of the existing Holloway Road Bridge. Click here to see a 1 minute video of the service bridge installation.
- Diversion of the utility pipes and cables to the service bridge. The utilities were all moved by Skanska just before Christmas 2016.
- Highway bridge deck demolition and replacement. This involved replacing the bridge deck which sits beneath the road, and strengthening abutments that support the bridge from below. This took place during a four day blockade of the railway line during Network Rail’s scheduled installation of overhead line electrification over the Christmas and New Year period in 2016. Click here to see a time-lapse video of the demolition and replacement of the bridge deck.
Project constraints and difficult conditions
The site is very constricted with Upper Holloway Station adjacent to the road bridge as well as many other premises including a church.
The railway underneath is the Gospel Oak to Barking Line, and its electrification required a bridge solution with significantly more headroom whilst still meeting significant highway alignment and tie- in constraints.
However, the major issue at the site was dealing with the multitude of services that were originally buried in the carriageway. To overcome this, the scheme required a service bridge which was put in place in June 2016 in advance works. The service bridge also serves as a footbridge for the station.
Throughout this project Ramboll and its JV partner WSP/PB provided full coverage and support throughout the demolition and the bridge reconstruction. Collaboration between all parties in the delivery team has been exemplary and is a tribute to the planning and commitment of the staff from TfL, Hochtief, the many subcontractors, and our design team.