The next phase of a major project to cut journey times between the north-east and Highlands is under way.
A total of £300million has been invested into dualling the track between Aberdeen and Inverness, adding thousands more seats and increasing the number of services.
This past summer the line between Aberdeen and Dyce stations was doubled over the course of 14 weeks.
And improvements have already been completed between Elgin and the north.
Now Network Rail and Bam Nuttall have started work on the next leg of the project, which will mean the line is dualled between Dyce and Inverurie.
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Groundworks have started to the north of the city with the first major element of the project an upgrade of the Don viaduct at Port Elphinstone.
The structure dates back to the Victorian era and requires strengthening if it is to accommodate the increased weight of more trains.
This work will begin in January and the overall project is expected to be completed by June.
In much the same way as this summer’s construction project, contractors will be required to work overnight as well as during the day.
Billy McKay, Network Rail’s senior programme manager, said it was a huge challenge to carry out a project of this scale.
He said: “It’s a live project, the management of something this size is a huge undertaking.
“We have made a commitment to deliver a safe and reliable project and we have had to keep in mind our land-side neighbours and keep them informed throughout the work.
“It’s all about improving the reliability of the service. Passengers want trains that are more frequent, are on time and are clean. And that’s what this will deliver.
“If we do what we set out to do in this short space of time it will be a remarkable achievement.”
The final phase of the work, which will dual the rest of the route between Aberdeen and Inverness, is scheduled to last from May to August 2019.
The new timetable, with increased services, will go live in December next year.
Next month there will be additional Elgin-Inverness services on the line.
There will be an extra 1,300 seats for passengers each day with a service between the two stops about every hour.
By May next year the majority of trains between Aberdeen and the Highlands will be high speed, with an additional 1,400 seats per day.
The final phase of the work will be finished by December next year where trains will run every half hour between Aberdeen and Inverurie during normal hours and every 20 minutes during peak times in the morning and evening.
There will be an extra 2,500 sears between the city and the town each day.