DUBLIN city centre is braced for five years of traffic and business chaos from major road works needed to build the Metro and Luas link-up line.
Luas chiefs have decided to dig up the city alongside excavation works on the Metro to Dublin Airport, starting at the end of next year.
Transport Minister Noel Dempsey said last night "it made sense" to have overlapping construction works to be carried out at the same time.
Luas chiefs admitted yesterday that construction work on the €170m link-up will cause disruption throughout the city centre.
The Railway Procurement Agency (RPA ) yesterday formally applied for planning permission for the long-overdue line linking the two unconnected Luas lines.
However, Mr Dempsey has insisted that the Metro must be built before the Luas link-up can proceed, but has agreed for the excavation and utilities work to be done earlier.
The route of the underground Metro and overground Luas link follow very similar paths.
By applying for the railway order yesterday, Luas chiefs plan to carry out the digging work in tandem with the Metro excavations.
The alternative is to dig up the city centre, build the Metro, and then come back and dig up the city in the exact same locations for the Luas link-up line.
Both projects are being carried out by the RPA.
Under the current plan, the Metro is due to be up and running by 2016, followed by the Luas line in 2018, according to the rail agency.
Tom Manning, RPA spokesperson, said yesterday that business interests in the city centre had been pushing for both projects to be built in tandem to minimise the expected disruption.
By seeking the railway order it was hoped that where parts of the Metro and Luas works overlapped it would be possible to carry out the works at the same time.
Mr Dempsey has insisted, however, that the cross-city Luas link line would not be built until Metro north is completed. The two big priorities for the Government are the Dart underground interconnector and the Metro.
The RPA is dependent on the Government for funding both projects, and it is clear that the Metro will get any cash allocations first.
The Luas line linking the St Stephen's Green and Tallaght services was due to be finished in 2012.
The new line will run from St Stephen's Green, down Dawson Street and down past Trinity College.
It will then travel down Westmoreland Street and O'Connell Street, before turning on to Parnell Street and then along Marlborough Street.
The route will cross the Luas Red Line at Abbey Street and then travel across the River Liffey via a new Marlborough Street public transport bridge. There will also be stops at Hawkins Street and College Street.
The project also includes a connection from the city out to Broombridge via Broadstone.