Silvertown Tunnel Project

 

Executive Summary

The Silvertown Tunnel Project is a scheme set to open in 2025 for the goal to provide an additional River Thames crossing to alleviate current traffic levels and congestion near the Blackwell Tunnel as well as regeneration on both sides of the river. TMS was tasked to do a Stage 2 Road Safety Audit (RSA) on the two-bore tunnel, the scheme is interesting as it had two vehicle lanes with one of the lanes being a dedicated large vehicle lane. It’s also interesting as it is to be the first Thames crossing scheme in over thirty years.

Introduction

Our client for this project was Transport for London, but the scheme is being delivered by a Special Purpose Vehicles Company to include finance, design, and construction of the project. The scheme which we were instructed to audit is a new two-bore tunnel under the River Thames in London to connect Silvertown on the North and Greenwich on the South side of the River Thames with new junctions at either end. The tunnel section itself will have two lanes in both directions, with one of the lanes being a dedicated Bus/Coach/HGV lane. The purpose of the scheme is to provide an additional River crossing to alleviate current traffic levels and congestion at the nearby Blackwall Tunnel as well as providing an opportunity for regeneration on both sides of the river. For the tunnel section and tie in junctions, TMS carried out Stage 2 Road Safety Audits, but in addition has carried out Stage 1 audits on the proposed Temporary Traffic Management schemes on the A102 and Millennium Way that will be necessary to facilitate the construction works.

Courtesy of Transport For London (Source: tfl.gov.uk/travel-information/improvements-and-projects/silvertown-tunnel)

Assessment

The scheme is quite varied in the sense that the two junctions at either end of the tunnel section are different. Due to this, the identified road safety problems were quite wide ranging. At the Silvertown Junction being a traffic signal junction, issues generally related to visibility of signal heads, see-through, queueing and exit blocking as well as fine details regarding the pedestrian crossings and signage. The issues identified would likely cause shunt and failure to stop, type vehicles collisions as well as increased risk in vehicle collisions with pedestrians and cyclists. At the northern end (Silvertown), a large traffic signal junction is to be provided to tie into the existing local road network and features facilities for pedestrians and cyclists.

At the Greenwich Junction, the free flow slip-road design brought altogether different issues, more to do with alignments such as weaving lengths and merges on bends. The issues identified at this location are more likely to result in merge, shunt, and sideswipe type vehicle collisions. The southern end (Greenwich), entry and exits to and from the tunnel portal will feed as free slip roads into the A102 which will also provide entry and exit to the Blackwall Tunnel. However, the tunnel itself (and portals) raised very few issues, most notable issues were about the lack of signage for pedestrian emergency escape routes.

 
 

Recommendations

As with the issues raised, the recommendations for the problems identified were varied for each element of the scheme. For Silvertown Junction by and large, the recommendations related to the design of the traffic signals ensuring adequate stopping sight distance to signal heads, providing cowls or louvers to prevent see-through and provision of high mounted traffic signal heads where three or more approach lanes were provided. For Greenwich Junction the recommendations were more to do with providing adequate sight lines and signage at merge locations.

Final Thoughts

Darren Newbold the auditor for the scheme found it to be a particular interest as it will be “the first new Thames River crossing to the east of Tower Bridge in over thirty years (Dartford Crossing being the last)”. This will also be the first time TMS have been involved in any River Thames crossing infrastructure. The initial site visit was interesting as the Audit Team were able to take the Emirates Cable Car, from which gave a superb overhead view of the alignment of the new tunnel. All in all, this is a unique scheme for TMS as a company to be involved in and for the auditors it will be interesting to see the scheme develop over the next few years, before having a drive through in 2025.

TMS Copyright 2013