The M1 Drogheda Bypass opened in June 2003. At an approximate cost of €254 million the project has been part financed by the Cohesion Fund of the European Union and by the Irish Government under the National Development Plan .

This new section of motorway links the Balbriggan Bypass at Gormanstown and the Dunleer Bypass at Monasterboice. The scheme involved the construction of 21.5km of dual carriageway, 7.5km in County Louth and the remaining 14km in County Meath with provision for widening to three lanes in both directions as traffic volumes increase. To enable traffic to enter onto and exit from the motorway four interchanges are provided at Gormanstown, Drogheda South, Drogheda North and Monasterboice.

The project also included the construction of 24 structures, including a high level bridge crossing the River Boyne.

Boyne Bridge
The Boyne Bridge is the first major cable-stayed bridge in Ireland, 350m long with a span of 170m. It incorporates a tall pylon at the south side with cable stays fanning out from it supporting the main structure. The bridge is located 3km upstream from Drogheda, where the ground level on the south side is much higher than that at the north, where it slopes down gradually. The area surrounding the bridge is environmentally sensitive, especially the reed beds on the north bank and the flora and fauna of Yellow Island in the middle of the river. North of the bridge, being right over the Battle of the Boyne site meant there was a need to avoid putting down large foundations. All of these problems were overcome by using a cable-stayed bridge. Although this option is more expensive, it can incorporate a much longer span without the need for supports in the river, thus protecting the river and the island from any interference.

Being very high above the river, crosswinds could cause serious problems and to avoid this transparent wind shielding is fitted to the bridge sides, offering motorists good views both upstream and down to Drogheda town. The deck is revolutionary composite steel and concrete design enclosed by glass-reinforced plastic, as steel if left exposed to the elements requires repainting to prevent rust.

Benefits of the Scheme
At a national level, the Drogheda Bypass provides a new motorway section of Euroroute E01 linking the major commercial seaports at Larne, Belfast, Dublin and Rosslare and the major airports of Dublin and Belfast. It also forms part of the Trans-European Road Network. The provision of a more efficient road network with completion of the scheme assists in greater reliability, greater traffic capacity and improved safety, leading to a reduction in journey time and transport costs.

At a regional level, the scheme forms an essential part of the strategic M1 motorway extending northwards from Dublin along the principal cross border route providing access to Belfast and Northern Ireland ports. As well as improving journey time and safety for traffic travelling between Dublin and urban centres in Northern Ireland, it also provides a service for towns in between such as Swords, Balbriggan, Drogheda and Dundalk.

At a local level the scheme provides an effective bypass of the town of Drogheda and the villages of Julianstown and Monasterboice, resulting in these urban communities benefiting both socially and environmentally from the elimination of long distance through traffic. The motorway also benefits the local industrial and commercial areas and the regional seaports at Dundalk, Drogheda and Greenore as well as facilitating the development of greater tourist activity, particularly in short stay holidays, by providing a more efficient road network with a greater traffic capacity and improved safety provisions.