An upgrade to the N4 dual carriageway between Leixlip and the M50 junction opened today.
The widening of the seven-kilometre route to three lanes in both directions is expected to substantially cut journey times between towns in west Co Dublin, north Kildare and the midlands.
The stretch of road has traditionally been one of the most notorious traffic bottlenecks on the western Dublin commuter belt.
The project to upgrade the route - which follows the existing N4 route south of Lucan village and north of Fonthill Road - commenced in September 2007 and was delivered on time at a cost of €75 million.
The National Roads Authority said one of the main objectives of the scheme was to “eradicate” the Newcastle road junction which was causing a major bottleneck.
The NRA said the route would improve access to Dublin Airport and Dublin Port.
The route was officially opened today by Minister for Transport Noel Dempsey who said the upgrade showed the Government's commitment to investing in top-class infrastructure, despite the State’s economic position.