The mainline rail journey between Inverness and the Central Belt could become quicker and more competitive in comparison with road travel - and carry as many as 200,000 more passengers a year - for an investment of just £55m.

This is the conclusion of two reports published yesterday on improving rail services in the Highlands. They claim that significant service enhancements on all of the railway lines in the north could be made for a relatively modest investment.

The reports are designed to influence railway strategy in the north up to 2020. They say that, at a cost of £55m, journey times from Inverness to Glasgow and Edinburgh could be cut by 44 minutes to 2hrs 45mins with hourly services.

The key works required include returning the four-mile stretch between Culloden and Daviot to twin track; building a passing loop at Ballinluig, along with general improvements; and work to Kingswood tunnel at Birnam Hill.

Taking an optimistic view, it is expected that in the first year around 138,000 passenger trips would result from the upgrade, rising to 200,000 by 2020. A good return on investment is expected, with every £1 generating a £2.61 benefit. More significant infrastructural work in Fife region could further reduce journey times to Edinburgh to 2hrs 30mins and would also benefit services to Perth, Dundee, Aberdeen and the north-east. The reports - commissioned by Highlands and Islands Enterprise (HIE), HITRANS (the Highland transport agency) and the Highland Rail Partnership - also consider possibilities for increasing freight and charter operations from Dingwall to Kyle of Lochalsh along with provision of a commuter service at a cost of around £1.4m.

The options for the Fort William and Oban lines include running separate trains to both places. Currently, the trains run together to and from Glasgow, splitting at Crianlarich. Two trains would have extra operating costs of £600,000 a year, and would be possible with the existing infrastructure. Line speeds could be improved at an estimated cost of £10 to £15m, which would also allow heavier freight.

Charlie King, chairman of HITRANS, said: "Rail is already an important driver in the economy supporting more than 1500 FTE [full-time equivalent] jobs. These reports help underline the further potential an enhanced rail network can give the Highlands."

Douglas MacDiarmid, HIE's director of global connections, said: "The enhancements proposed represent very good value for rail projects in a UK context and would deliver significant economic benefits for the north of Scotland."

Ron McAulay, Director of Network Rail in Scotland said: "These reports will feed into the process of compiling a future strategy for Scotland's growing railway."