Challenges and Solutions
Due to the highly congested nature of Abbey Wood station, one major challenge for FM Conway was to maintain a safe, yet efficient two-way traffic flow across the flyover to ensure that the works ran smoothly with minimal disruption to the public. This was achieved through phased working, alleviated by the support of FM Conway’s in-house Traffic Management division.
Contraflow traffic lanes were designed and implemented to keep the traffic moving. As the project was designed to widen the existing carriageway, TM arrangements maintained the daily traffic flows. Temporary signals were used to manage traffic at roundabouts, during key phases of work and to provide pedestrians with safe crossing locations. All TM was designed by our in-house team and approved by one of FM Conway’s in-house Traffic Safety and Control Officers (TSCO). Installation was undertaken by FM Conway’s specialist TM division who are all Lantra certified and all on site changes were in accordance with Chapter 8 of the Traffic Signs Manual.
Dedicated TM site meetings with TfL, Bexley, Greenwich, Peabody, Thistlebrook, TfL Buses and third-party contractors were utilised to review arrangements, future plans and provided an opportunity to identify improvements and address potential risks. Through site meetings we were able to improve access and egress to third party works, in addition to rephasing our TM to accommodate changes to the programme and sequencing of the works. Our site team was responsible for undertaking three daily inspections, any improvements were implemented immediately, and issues rectified.
Our TM design process incorporated route plans for deliveries and collections which were circulated to drivers on a daily basis. Site access and egress was carefully planned to minimise disruptions on the network by including site vehicle movements into the works area, in a controlled manner. Site entrances were clearly and visibly signed to prevent unauthorised access.
An additional challenge was managing the concrete works on an elevated deck, which saw the development of a bespoke cantilever scaffolding design to support the team. The access scaffold was three boards wide, drilled into the outside of the existing parapet. From these platforms, the new parapet access was used to construct the new concrete rap around the existing parapet, allowing the replacement of the existing expansion joints. This was established using cherry pickers and alloy towers, allowing the team to effectively and safely set up at an appropriate height.
As the footways and carriageways were constructed on an existing bridge deck, depth was restricted to achieve new finished levels. Therefore, drainage was incorporated into bespoke iron channel kerbs to ensure the successful installation of a modernised drainage system. The bridge deck’s depth restrictions proved further challenges for the team when installing new columns for street lighting and signage. The overall depth of the bridge deck was less than 300mm to the new paved surface level, therefore FM Conway installed shallow NAL socket foundations – 245mm deep – in a concrete base, directly behind the kerb drains to install the new columns.
Due to the limited construction depth on the flyover, FM Conway’s technical team worked in collaboration with the Council to introduce our proprietary single layer surfacing solution, SureLayer, which incorporates a chemically engineered polymer modified bitumen to provide enhanced durability and greater resistance to common failure mechanisms such as rutting and cracking. The elimination of a horizontal joint also improves compaction and minimises water ingress to retain the structural integrity of the road pavement. SureLayer was laid at a depth of 70mm in lieu of the traditional 100mm dual layer specification. In addition to realising a direct cost saving of 8.7% on the surfacing works at Harrow Manorway, this material innovation reduced time on the network by 43% and congestion by 27%.
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