Given Tara's cultural significance and national monument status, it is not surprising that the Irish government met resistance when it announced plans for a 60 km road running straight through the Gabhra Valley between Tara and the nearby Hill of Skreen. Archaeologists and historians claimed that the entire valley, not just the hill, contains historical monuments and artifacts and should therefore be protected. In its defense, the National Roads Association (NRA) argued that a new road was necessary because the existing N3 highway is deteriorating, thereby making travel dangerous and inefficient for drivers between Dublin and Navan. A deal was signed with Eurolink, an independent contractor, and construction began in Spring 2006.
This is a good article on the history of this project.