A significant new contract for work to improve the railway between Aberdeen and Inverness has been announced by the Scottish Government agency Transport Scotland.

It has appointed BAM (www.bam.eu) as the principal contractor for the £170 million upgrade — more than 20 years after hopes for a route upgrade were originally aired.

The announcement came as members of the Scottish National Party (SNP) gathered in Aberdeen for their annual conference. The SNP Scottish Government says it is funding the enhancement to transform journeys on the route. A half-hourly commuter service is planned between Aberdeen and Inverurie, with additional peak services running between Inverness and Elgin.

The proposed improvements will also see reduced journey times between Aberdeen and Inverness. The Beeching report of 1963 spared the line but recommended closure of the now very busy intermediate station at Inverurie.

In the 1970s, much of the double track was reduced to single track with passing loops — often at awkward places — that caused delays. Significant sections of the line will now see double track restored.

BAM recently completed — on time and on budget — the £294 million Borders Railway. The first phase of the Aberdeen-Inverness enhancement — due for completion in 2019 — will see 16 miles of track between Aberdeen and Inverurie doubled, a new station built at Forres, and the platforms at Elgin and Insch extended. Signalling along the route will also be upgraded.

Infrastructure will be altered to allow space for new stations to be built at Dalcross (near Inverness) and Kintore (at the Aberdeen end of the 108-mile route). Plans for these new stations are being developed separately by two regional transport partnerships (Hitrans and Nestrans).