N7 Naas Road Improvement

Ireland

Project outline

Located east of Naas in County Kildare, Ireland, the scheme links with the M7 motorway and provides one of the two main east-west approaches into Dublin.

Contract value

£75M

Key features

• A key aspect of the design focussed on the need to facilitate continued flow of 70,000 vehicles per day by minimising the impact on the existing network.  To support this objective, the scheme was constructed in two separate phases thereby minimal disruption on the N7 and the communities local to it.
• There was a requirement for the scheme to be completed and opened to traffic in time for the 2006 Ryder Cup.  To help facilitate completion of the mainline before the event commenced the design maximised the length of off-line construction and incorporated a standardised approach to the design of structures in order to expedite the design process.  This entailed a single span design that could be installed in a single overnight operation, whilst the alignment design of approach roads were revised to compliment proposed bridge spans.
• Departure needed to use TWC therefore alleviating increased pavement costs and mitigating road noise. NRA precluded use of TWC.
• FM rationalised the proposed junction layouts at Steelstown and Castle Warden. to remove full grade separation in favour if compact grade separation.
• Slip roads were designed to accommodate full N7 mainline traffic flow so that traffic could be diverted up slips whilst works were undertaken on the mainline.
• Significant side road provision was made to ensure linkage between existing farm accesses and the local road network. The area adjacent to the scheme corridor was dominated by agricultural land, and the provision of new local access roads were supplemented where necessary by accommodation works.
• Req. for noise barriers, Inherited design located these in highway verge meaning safety barrier protection and visibility obstruction. Fm identified alternative product that could be situated beyond protection/visibility zone therefore reducing costs and potential safety issues.
• Contract stated 1km length of rigid concrete pavement needed replacing with flexible pavement.  Broke up pavement, removed steel r/c and used as capping for new flexible pavement therefore saving new material/haulage
• Innovative approach to managing submission of design reviews therefore ensuring no ‘surprises’ at Design Certification prior to construction. Overall programme 30 months. Actual duration 22 months. 3 months saving on design.

Skills utilised

• ECI Procurement
• Project Management
• Multidisciplinary project coordination (Integrated design management)
• Partnering approach
• Value Engineering and design optimisation
• Stakeholder communication and Public Consultation
• Engineering design (highways, drainage, pavement, structures etc.)
• Landscape and Environmental coordination and management
• Preparation and publication of draft statutory Orders
• Public Inquiry and provision of expert witnesses
• Risk Management
• Cost Management

Project detail

Roughan & O’ Donovan Faber Maunsell Alliance was engaged by Clonmel Laing O’Rourke as their designer for the N7 Naas Road Widening and Interchanges scheme.

• Project includes for 14.5km on line widening from dual 2 to dual 3.
• Four new grade separated junctions.
• 14.5km side roads.
• Extensive utility diversions.
• Complex traffic management schemes.
• Two Footbridges.
• 15 Sign Gantries.
• Extensive None Mitigation Measures.

The design was driven by the need to facilitate continued flow of 70,000 vehicles per day through the site and to maximise use of the existing pavement construction while upgrading for 40-year design life.