MORE than 80,000 motorists face disruption for the next three weeks as construction work begins tonight on a major upgrade of one of the busiest junctions in the country.
Drivers of some 80,000 vehicles who cross the junction will face delays at peak times for up to three weeks as traffic is shifted onto new lanes.
The National Roads Authority (NRA) said traffic volumes would be monitored daily to ensure delays were minimised.
A spokesman said: "At peak times, there could be significant delays due to the time needed for traffic coming off and onto the Belgard and Fonthill roads. The delays will primarily impact on traffic coming to and from Dublin."
The changeover will begin at 9pm and will involve traffic heading from the M50/Red Cow interchange toward Naas (westbound) being shifted to a new three-lane road to their left.
In three weeks' time, traffic coming east from Naas will be moved across the 'old' westbound road, allowing construction to be begin on the flyover.
The scheme is part of the €282m Newlands Cross/Arklow-Rathnew bypass construction package, which is being built under a public private partnership by BAM Civil Ltd.
Tolls will not be imposed on motorists.Both are expected to be completed by the end of 2015, with the Newlands flyover likely to be opened in the spring.
The flyover will allow three lanes of traffic in each direction and also includes space for the deferred Metro West which is designed to run from Tallaght to Dardistown near Dublin Airport.