A major project to upgrade the tunnel at Glasgow Queen Street train station has been completed ahead of schedule.

The £60m programme, which began in March and has now finished almost three days early, created more than 4km of new rails with the addition of 1.8km of concrete slab track.

The platform layouts have now been changed and train services will be reintroduced over the weekend.

Transport minister Humza Yousaf helped tighten the final bolt on the new slab track inside the tunnel on Friday.

He said: "I am pleased to see the work on the Queen Street tunnel completed ahead of schedule and on budget.

"This has been an unprecedented project, both in engineering terms and in the scale of the operation required to keep people moving and services diverted via the underground platforms during the works."

The work is part of a larger programme to electrify the rail line between Edinburgh and Glasgow.

Mr Yousaf added: "This is a key milestone in our programme of investment for Scotland's railways and literally paves the way for the introduction of a new generation of electric trains.

"I would like to congratulate the ScotRail Network Rail Alliance on a successful job and the hundreds of men and women who have worked day and night to deliver the hugely ambitious project.

"I would also like to thank the passengers who have had to alter their plans for the duration of these works for their patience."

Journeys have taken longer and services have been less frequent as the work has been carried out.

Phil Verster, managing director of the ScotRail Alliance, said: "The successful, early delivery of this project will allow us to introduce faster, longer and greener trains on the main Edinburgh to Glasgow line - delivering thousands of extra seats, shorter journey times and improved accessibility for customers.

"This was a massive engineering challenge and it was only through the careful planning and professional delivery of the project team that we have been able to complete this vital investment in Scotland's railway ahead of schedule.

"I would also like to thank all of our customers who have shown great patience and understanding during the last five months."