A40 Pembrokeshire
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A40 in Pembrokeshire -Penblewin to Slebech Park

Client: Costain/Welsh Assembly Govt.

Value: £3m


  • 2.0 km Carriageway widening
  • 2.6km new bypass
  • 170m segmental retaining wall constructed
  • Major Waterways management for River Cleddau during construction


The length of A40 between Penblewin and Slebech Park in Pembrokeshire had for many years been regarded as unsatisfactory. Poor carriageway design was causing accidents, while the narrow stretch leading through the village of Robeston Wathen effectively cut the community in two and created noise, congestion and pollution. In line with its One Wales commitment to investing in the transport infrastructure, the Welsh Assembly Government decided to improve the road with a view to cutting journey times and enhancing road safety, diverting through traffic away from the village on to a new bypass.


The £30 million project was a huge undertaking that involved widening 2km of existing carriageway as well as building the 2.6km bypass. It included four bridges, three underpasses, two new roundabouts, a 170m-long retaining wall and fourteen culverts. For the first time in Wales, a ‘2+1’ format was used for the carriageway to provide safer conditions for overtaking. Since the road passes through an environmentally sensitive area, extensive environmental mitigation works were required. The project was completed on schedule and within budget by a team that displayed an excellent attitude to partnership and team working, demonstrating the benefits of using the ECI form of contract. Journey times have been improved while safer overtaking opportunities and protected crossings for cyclists and pedestrians have enhanced safety. The village of Robeston Wathen has benefited from greatly reduced traffic flows of up to 90 per cent, which has cut traffic noise and improved air quality. Meanwhile, the co-ordinated approach to biodiversity resulted in a range of environmental mitigation measures that satisfied all the statutory consultees. These included five water treatment ponds, wild mammal-resistant fencing, landscape integration and safeguarding of four essential mitigation areas.

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