Grontmij is lead designer on the first motorway widening project in Ireland - a Design and Build (D&B) contract to carry out online widening to a 7.5km section of the M50 Dublin orbital motorway from dual two-lane to dual four-lane motorway. It also includes the upgrade of three interchanges to facilitate free flowing traffic movements.

Optimised design

The tender design incorporated extensive revision to the specimen design, including deletion of a seven span viaduct and converting a three level interchange with the N7 to 2 levels, to reduce costs. The project also included extensive post-award redesign of the N7 junction, including realignment of the existing Luas Line, to provide a full free flow interchange.

Pavement testing

Grontmij’s involvement included detailed pavement design, incorporating insitu falling weight deflectometer testing, residual life assessment and optimised overlay design for the existing carriageway. The consultancy also undertook investigations into re-use of the existing pavement foundations.