The project will establish the business case for reducing journey times, increasing capacity and enhancing freight operations on the route, which links the Highlands with Scotland’s Central Belt and the cities of Glasgow and Edinburgh.

The work is being carried out as part of the Highland Main Line Upgrade Phase 2, which is expected to cost up to £250m.

The long-term aim of the project is to reduce the fastest Inverness - Edinburgh journey time from 3h 18min to 2h 45min with an average journey time of three hours and hourly services by 2025.