Fife Council is in a race against time to replace a badly corroded road bridge before the Levenmouth rail link opens next year.
The major works will close the Leven Rail Bridge, also known as the Bawbee Bridge, for up to a year.
And rail campaigners fear it could hold up the return of trains to the area.
The 75-year-old bridge is the main route between Leven and Methil and carries around 18,000 vehicles per day.
It spans the River Leven, as well as the route of the new railway.
But it is in a poor state of repair and has a limited lifespan.
Experts say postponing the work until after the rail link opens would push the cost up from £8.15 million to more than £13m.
However, the project is expected to take 47 weeks and there are concerns any delay would affect the delivery of the railway – due to open in December 2023.
Alarmed campaigners are now seeking assurances that the Levenmouth rail project remains on track.
New temporary road bridge proposed during works
Meanwhile, the bridge closure will impact hugely on traffic.
Council officers have proposed building a new temporary bridge across the river during the closure.
Otherwise, drivers face a five-mile diversion through roads incapable of carrying the additional vehicles.
The preferred option involves creating a new roundabout on South Street, Methil, and directing traffic past Bayview Stadium.
Ross Spiers, the council’s structural services manager, says doing nothing is not an option.
“The existing bridge is in a deteriorating, poor condition,” he said.
“The need for the full replacement of the Leven Rail Bridge has now been identified with an estimated overall cost of £8.157m.”
And he added: “The Leven rail link is programmed to be reinstated by December 2023.
“This timing places a need for the council to deliver the bridge replacement works before the rail link is implemented.”
Levenmouth rail link means bridge needs more work
The council first proposed strengthening the bridge in 2006.
At that point it needed a new deck but the £2m of work didn’t go ahead.
Now, because an electrified railway line will run beneath it, the work needed is more extensive and the price has rocketed.
As well as a deck, the bridge needs new higher parapets to allow trains to travel underneath.
And new abutments are needed to support it at each end.
To avoid “contractual complications and uncertainties”, the work will be incorporated into the rail link project.
Mr Spiers added: “With the Levenmouth rail link programme to be delivered by December 2023, delivering this project as a stand-alone traditional tendered contract would result in the works not being completed in time for the December 2023 deadline.”
Funding options are still being explored but councillors will be asked to approve the work next week.
