By lyndamyer
A two-way tram system, an extension to the Docklands Light Railway (DLR) and improved walking and cycling links are among the suggestions for better uses of the Silvertown Tunnel by Green Party London Assembly member Sian Berry.
The Silvertown Tunnel is Transport for London’s (TfL) new four-lane road crossing beneath the River Thames being constructed by Riverlinx CJV (Bam Nuttall, Ferrovial, SK ecoplant) that will take strain off the overused Blackwall Tunnel and provide more capacity for new bus routes across the river.
The tunnel boring machine (TBM) is currently driving the first of the 1.1km twin-bored tunnels and Riverlinx project manager Ivor Thomas recently told NCE that it will have passed safely under the Thames by Christmas. Once its first drive is complete, the TBM will be rotated 180° and it will drive back under the river, creating the second bore. The tunnel is expected to come into operation in 2025-26.
However, Berry and the Green Party are in opposition to the construction of the tunnel and creation of more road traffic in the area. While accepting that it is too late to stop the first bore, Berry has canvassed opinions on what could be done with a single bore tunnel that would provide green alternatives to the full scheme. She has compiled the best suggestions into a report titled Better Ways to Use the Silvertown Road Tunnel.
The suggestions are as follows:
A new two-way tram link from Newham to Greenwich through a single-bore tunnel
This would run from Canning Town to development areas in Greenwich and Thamesmead, running along the busway corridor on Millennium Way and then along bus lanes into Charlton. It is estimated that this could carry around 4,500 people per hour during morning peak hours, whereas the proposed Silvertown buses would only carry around 1,200.
It could be funded by the money saved from not making the second tunnel bore. Using the existing busway would also reduce the additional infrastructure needed. But for a high quality tram system, investment in tracks, stops and technology would be needed, in addition to running costs. It is suggested that something similar to the £30-40M annual subsidy for Croydon’s tram system would be necessary.
A tram system would have a low environmental impact as it runs on electricity. It would have significant social benefits to people in the area who are dependent on cars and have low access to public transport.
A DLR extension using the single bore tunnel, running from Canning Town to Kidbrooke
This has been proposed before and in 2012 Greenwich Council commissioned studies into the public transport options for Silvertown Tunnel. The results showed an extension as far as Eltham was likely to attract the largest patronage, offer the best and most reliable journey times, provide the most capacity and be the safest solution, while providing the seamless interchange with several mainline rail services and the existing DLR network.
This extension from Canning Town to Kidbrooke would use the A2/A102 road corridor heading south from the Greenwich peninsula, with the potential to extend it to Eltham and Falconwood. This would require narrowing of the lanes along these roads and building the railway above the central reservations.
The feasibility study estimated use by 17-21M passengers annually, which is far higher than the 1.3M bus passengers expected to use the Silvertown Tunnel currently.
Once again, money saved from not creating the second bore could be used to fund this scheme. However, there would also need a large investment to create the new infrastructure for the reminder of the route. The 2012 estimate for the entire scheme was £818M.
As an electric service, its operational pollution would be minimal. However, construction of the new stations and elevated sections of track would require a lot of concrete and associated embodied carbon. Its social impact would be even greater than the tram option.
A single-bore tunnel repurposed for a high-quality walking and cycling link
The suggestion is to create a high quality walking and cycling link that would connect to the existing cycling network. This would take the strain off the nearby Greenwich Foot Tunnel, which is suffering from high demand and limits to reliability due to problems with lifts. Pre-pandemic, capacity at the Greenwich Foot Tunnel was forecast to be reached through peak hour before 2025.
It is also proposed that the Silvertown Tunnel TBM could be diverted after completion of the first bore to add a further tunnel at the location of the proposed Rotherhithe to Canary Wharf bridge to create links on both sides of Canary Wharf.
Busy parts of London’s cycleway see 2,000 cyclists at peak hour, and it is expected that this tunnel would see the same level of traffic.
It is estimated that this scheme could be completed within the costs saved from abandoning the Silvertown Tunnel after one bore.
This would provide a significant social benefit as there are few walking and cycling options to cross the river in this location. It would also be free as compared to current methods for reaching Canary Wharf from south east London, which require fares.
It is suggested that ambulances could use the cycle and walking tunnel if necessary to avoid congestion.
A single bore tunnel with a revised internal structure to enable multiple tiers and different modes at each level
The size of the bore of the Silvertown Tunnel is suggested to be enough for a double decker solution for different modes of transport. The current design has a lot of space taken up by a very large ventilation system, but this could be removed if the tunnel were not to be used by road traffic. If it is used for walking, cycling, trams or DLR trains the fire risk would be lower and therefore less ventilation necessary.
It is suggested that a DLR or tram could go in the top deck, as there is a lower clearance necessary than for HGVs, which is what the tunnel is currently designed for. Therefore, the deck could be moved up slightly to make space for a low-level walking and cycling route and the additional separate ventilation system. The lower level could also be used for emergency access and evacuations.
Alternative uses for a twin-bored tunnel
If the second tunnel bore goes ahead, Berry’s report suggests combining any of the two above options to create multiple new options for crossing the river. This would combine all the capacity estimates and social benefits, though the overall cost would be higher.
Another suggestion is to convert the northbound Blackwall Tunnel into a walking and cycling route. The northbound traffic would instead go through one of the new bores at Silvertown. The other Silvertown Tunnel bore would be used for one of the options outlined above.
A TfL spokesperson said: “The Silvertown Tunnel will provide a public transport-focused river crossing with new, zero-emission bus links across the Thames. Once open, the crossing, which is within the Ultra-Low Emission Zone and will be subject to a user charge, will also reduce congestion and improve the reliability and resilience of the Blackwall Tunnel and further improve overall air quality in the local area.”
“Construction on the tunnel is now well underway, with the tunnel boring machine having already completed 70 per cent of the first tunnel and will arrive at the rotation chamber in early 2023, before being rotated and tunneling back to Newham. The tunnel remains on track to be completed in 2025. We will continue to engage with the local community and monitor traffic, air quality and other factors, both during construction and once the tunnel is open, to ensure that overall traffic volumes and associated emissions do not increase,” TfL said.
