Train users will face 20 weeks of diversions and new timetables when Glasgow Queen Street High Level closes on March 20.
Work is being carried out in the tunnel, near Scotland’s third busiest railway station, as part of a £60 million upgrade to provide faster and longer trains at Queen Street High Level.
The closure will allow major engineering works to renew 1800m of existing concrete slab track, which carries the rails through the 918m-long tunnel.
It is the largest engineer-ing project carried out on the Glasgow to Edinburgh railway line since it was built, involving 140 days of round-the-clock working, half a million man hours, the removal of 10,000 tonnes of concrete slab and 4000m of new rails.
The infrastructure to carry the overhead electrification system through the tunnel – part of the Edinburgh Glasgow Improvement Programme (EGIP) project – will also be installed.
A £742 million investment into Scotland’s railways has been on-going in the central belt since 2014.
It has already seen Haymarket Station refurbished and extended, the electrification of the Cumbernauld to Glasgow line and bridges in Linlithgow and Falkirk being demolished and rebuilt, so electrification work can be completed.
Construction of the new Edinburgh Gateway Station should be completed by December 2016, with an all-electric fleet running on the Edinburgh and Glasgow line by December 2017.
A 42 minute service between the two cities should be in place by the end of 2018 and the redevelopment of Glasgow Queen Street station is likely to be unveiled in March 2019.
Transport Minister Derek Mackay said: “This is a once in a generation project and one of the most ambitious ever planned on the Edinburgh to Glasgow route.
“The works will support the introduction of a new generation of faster, quieter and greener electric trains on routes across the central belt next year.
“Although I understand that this work will cause some inconvenience to passengers, the ScotRail Alliance is working to ensure that services are maintained where possible, disruption is kept to a minimum and passengers are kept well informed.”
ScotRail has flooded the public with information to make sure everyone is aware of the closure and how it will affect their commute.
Managing director Phil Verster said: “It’s our biggest ever public information campaign.
“In the run up to the closure we’ve spoken directly to our customers, giving them the information they need and answering any questions they have.
“The benefits of this investment will be considerable, not just for our railway but for the country.”
New timetables have been available online since February and printed versions will be in stations from the second week in March.
An interactive map highlighting new journey routes is also available online, showing exactly how routes will change.
Some services will see the frequency of trains reduced from four per hour to two. Other journeys are expected to take an extra 25 minutes and some involve boarding two different trains to reach a destination.
A one-way queuing system is also being introduced to keep Glasgow Queen Street Low Level passengers safe during the 20 week closure.
Customers will be directed to queuing areas, then guided to the platform when their train arrives.
Passengers for Airdrie, Bathgate (and stations on this line), Croy, Cumbernauld, Falkirk High, Linlithgow, Polmont, Edinburgh Waverley, Haymarket, Oban, Fort William, Mallaig and Lenzie (5.31pm and 6.01pm services only) will enter via Dundas Street and exit to North Hanover Street.
People travelling to Bishopbriggs, Lenzie, Larbert, Stirling, Dunblane, Alloa, Perth, Balloch, Milngavie, Helensburgh, stations via Yoker and stations via Singer will enter on North Hanover Street and leave via Dundas Street.
The entrance to the station from George Square, on West George Street, will still be open but customers will not be able to use this entrance to access the Low Level station.
Passengers are also being advised to arrive ten minutes earlier than they normally would to board their train.
The fastest route for Glasgow to Edinburgh is via Bathgate and Airdrie, with four trains per hour, taking 70 minutes.
Customers from Linlithgow, Polmont, Falkirk High and Croy will be diverted to and from the low level station with two trains per hour, taking an extra 25 minutes. There is also one train every two hours between Glasgow Central and Edinburgh via Motherwell and Carstairs, with a journey time between 60 and 70 minutes. Journeys from Stirling to Glasgow will take an extra 25 minutes on a diverted route. A new hourly Falkirk Grahamston to Anniesland service, via Cumbernauld and Springburn, will run during the closure. Change at Cumbernauld or Springburn for connections to Glasgow.
Cumbernauld will be reduced to two services per hour, one direct to Glasgow, the other requiring a change at Springburn.
Anniesland to Glasgow via Maryhill is reduced to an hourly service. Passengers from Ashfield, Possilpark and Parkhouse, Gilshochill, Summerston, Maryhill and Kelvindale will have a choice to make: travel west towards Anniesland, change trains there to reach Queen Street, or catch the eastbound train for Falkirk Grahamston, changing at Springburn.
During the tunnel closure there will also be fewer peak services. The average journey time between Edinburgh and Glasgow will be 70 minutes.
The actual number of seats in peak time rail journeys will, however, remain the same asScotRail has redistributed the carriages. More information can be found at www.scotrail.co.uk/queenstreettunnel.