Commuters travelling to work in Edinburgh or Glasgow face weeks of delays when a major railway engineering project begins on Saturday.
The Winchburgh tunnel in West Lothian will close for 44 days as part of the £742 million Edinburgh-Glasgow Improvement Programme (EGIP), which will allow faster journey times on the main line.
The route - one of the busiest in the UK - is being electrified to allow the use of faster trains which ScotRail claims will reduce journey times by as much as 20 per cent as well as providing more seats.
Engineers will lower and relay two lines of track through the 330m tunnel and install equipment to carry the overhead power lines needed for the electrification of the railway.
The tunnel will remain closed while work continues 24-hours a day. It is scheduled to reopen on July 27 in time for the festival season in Edinburgh.
Passengers are advised to set off at least 20-25 minutes earlier than usual as journeys from all Falkirk district stations are expected to take longer.
This work is a vital part of transforming our railway, and the benefits will be felt for generations to comePhil Verster, ScotRail Alliance managing director
Those travelling to Edinburgh will experience the most disruption, with replacement bus services or diverted trains required to reach the capital.
Direct trains to Glasgow will remain but with reduced frequency and delays likely.
Season tickets and travel cards will be valid for all replacement services.
Falkirk High to Edinburgh Waverley/Haymarket: Two trains an hour to Linlithgow. Passengers will then board either a replacement bus service or another train. At peak times this is likely to be a bus.
Polmont to Edinburgh Waverley/Haymarket: Two direct trains per hour, via a diverted route. These services are likely to be very busy at peak times. An additional two trains will call at Linlithgow, where passengers will likely join a replacement bus service at peak times or a diverted train.
Falkirk High/Polmont to Glasgow Queen Street: Two direct services per hour, trains may depart at different times, take longer than usual and will be busier than normal. ScotRail advises passengers to set off 20-25 minutes earlier than normal.
Larbert/Camelon/Grahamston to Edinburgh Waverley/Haymarket: Services will be diverted and will take approximately 25 minutes longer. ScotRail advises passengers that trains calling at Camelon and Grahamston are likely to be extremely busy at peak times, and passengers may not be able to board.
Larbert/Camelon/Grahamston to Edinburgh Park: Passengers will change at Linlithgow to board a replacement bus to Edinburgh Park.
No trains will call at Falkirk High on Saturday, June 13, and on each Sunday until July 26 due to engineering works. Service to Glasgow Queen Street will instead leave from Falkirk Grahamston. A replacement bus service to Edinburgh will depart from Grahamston car park and call at all intermediate stations, including Polmont.
Additional weekend work will also take place before and during the tunnel closure period.
Customers are strongly advised to check the ScotRail website before travelling for up-to-date travel information.
Phil Verster, ScotRail Alliance managing director, said: “This is a massive piece of work that will help deliver long lasting benefits to our customers. Electrifying the line between our two biggest cities will allow us to run faster, longer and greener trains that will cut journey times and increase the number of seats available on this key route.
“We need to improve the line and install the equipment that we will need to run these new and improved trains, which will cause unavoidable disruption.
“This work is a vital part of transforming our railway, and the benefits will be felt for generations to come.”
Tunnel closure will allow faster journey times... eventually
Following electrification of the main line, new seven-carriage electric trains will be introduced from December 2016 replacing the existing six-car diesels.
New electric trains will be delivered by December 2017, and further capacity enhancements will follow in December 2018 when eight-car trains are introduced.
The use of electric trains will improve journey times as they offer higher acceleration than existing diesel trains.