MORE than five million train journeys face disruption while Queen Street Station is closed for four months.
Last week, Network Rail confirmed the upper-level station would be shut entirely to allow the slab track in the tunnel to be replaced.
The news came a day after plans were unveiled for a £120 million redevelopment of the station, which will also cause major disruption.
New figures for passenger journeys show that more than 25% of all trips involving Glasgow stations either start, end or transfer through Queen Street Station.
In 2012/13, Queen Street handled 16.45 million passenger journeys. All 58 stations in Glasgow dealt with a total of 67.7 million trips.
Of the Queen Street journeys, 1.5 million involved changing to another train at another station.
Central Station was the busiest, with 27.1 million journeys - an increase from 26.6 million the previous year.
The Queen Street figures increased from 16.37 million in 2011/12 to almost 16.5 million, equating to an average of 1.37 million trips a month.
Seven other stations - Anniesland, Anderston, Charing Cross, Exhibition Centre, Hyndland, Mount Florida and Partick - handled more than one million trips in the past year.
Network Rail has not decided which months the station will be closed, stating only that it is likely to be in 2016.
Some of the services from Queen Street during the maintenance work will be diverted to Central Station, putting even more pressure on one of the busiest stations in the UK. Passenger groups said the extent of the disruption and alternatives must be outlined to the travelling public as far in advance as possible.
In the same year, work to redevelop the station will also take place, with a reduction in platform capacity and restricted access for three years until completion in 2019.
Robert Samson of Passenger Focus said the work will be one of the biggest undertakings on the UK's rail network in recent years.
He said: "It is going to be very difficult to manage the number of passengers who use the station.
"One of the key issues is getting information to passengers in advance and, for the redevelopment, about access to the station - especially for disabled people.
"We have published our report on what passengers expect during works.
"Passengers will put up with disruption if it means improvements, but it depends on how long it lasts.
"It is going to be one of the biggest and longest closures of a main station in recent years.
"Reading was closed for a while but not for that length of time."
Network Rail said the exact details of the closure and works were still to be finalised, but it was expected to take place in 2016.
The firm said more details would be available once it had been decided which services would be redirected and to where.
Business leaders and local traders have warned of the impact on custom, with many reliant on passing trade to and from the station.