Rail passengers doubtless welcomed the recent news that Transport Scotland had awarded a £10m contract for upgrading crossing loops at Aviemore and Pitlochry as part of a wider £57m programme to enhance the largely single-track Highland Main Line (HML) from Perth to Inverness. But - compared with the steady progress of the £3bn dualling of the parallel A9 road - is that rail funding enough to make trains fully competitive with the car, the coach and the lorry?

Trace the history back to 2008, when the Scottish Government's 'Strategic Transport Projects Review' (STPR) identified upgrading the HML as one of four top priorities among 29 schemes across Scotland. Investment of between £200m and £450m was envisaged, including "additional loops, dynamic loops or lengthening of double track sections" - a far cry from the works now underway.

The upgrade of just two loops, which is driven entirely by ScotRail's new timetable - in combination with the introduction of refurbished High Speed Trains and cutting out stops south of Perth - is intended to secure an average passenger train time-saving of 10 minutes between Edinburgh/Glasgow and Inverness, plus an enhanced hourly frequency of train service between Perth and Inverness.

These quantitative improvements will satisfy Transport Scotland's 2012 'High Level Output Specification' requirement from the rail industry for the 2014-19 period, which also requires the industry to achieve the rather vaguer target of "more efficient freight operations" on the Highland Main Line. So what will the current upgrade do for rail freight and its efforts to keep heavy lorry traffic off the A9?

In practice, very little. The crossing loop to be extended at Aviemore was already the longest on the line, and at Pitlochry - the shortest loop - there will be no extension, so lengthy freight trains will get no benefit. The Class 66 locomotives which haul the daily Stobart/Tesco container train from Central Scotland to Inverness have enough power to pull a train of 28 containers - the equivalent of 28 lorries - but the lack of long crossing loops restricts the operation to just 20 containers. So rail is 30 per cent less efficient than it should be.

Signalling improvements at Aviemore and Pitlochry may, in theory, offer some time saving for freight trains - but the two enhanced loops will be occupied by the hourly passenger train service for most of the day!

A much brighter future was promised for rail freight back in the 2008 STPR document, based on: "provision of bi-directional signalling to reduce the impact of engineering works on the route (permitting the route to remain open for freight throughout the day and week); increased length of freight loops (allowing longer freight trains); and removal of speed limits below 75 mph Permanent Speed Reductions (PSRs) for freight trains". The outcome would be that: "the freight improvements would make it considerably more attractive for freight hauliers to move containers and other goods by rail, by reducing journey times".

So modest is the Scottish Government's current plan for rail freight infrastructure improvements on the HML that there is a real danger that A9 dualling will, in practice, lead to a switch of freight from rail to road - the opposite of government policy.

A Scottish national newspaper revealed last year that an expert report commissioned by the Scottish Government - which Ministers did not intend to publish - concluded that 80 more lorries a day would travel the A9 in each direction by 2025, but rail freight's share of the market would drop by one tenth.

The report - released in response to a Freedom of Information request - concluded that: "Realistically, the shorter journey times and improved reliability offered by A9 dualling will lessen the potential switch from road to rail and all other things being equal, likely to constrain future rail freight growth."

In its defence, Transport Scotland is making noises about further improvements in a "next phase" of rail upgrading after 2019 - but how long can the freight railway afford to wait without seeing serious A9-inflicted damage to its existing core business?

In the admirable 2017 High Level Ouput Specification for the 2019-24 period, Scottish Ministers "require all reasonable steps to be taken to facilitate growth of 7.5 per cent in rail freight traffic carried on the Scotland route, of which, at least 7.5 per cent will represent a growth in new business (i.e. new traffic flows, not previously moving by rail)". Achieving that growth on the ground - and avoiding loss of existing freight traffic from rail to road - will be the real test of government policy.

Along the Highland Main Line in particular, the rail freight industry needs serious infrastructure investment so that it can compete more effectively against road haulage - and deliver the significant economic and environmental prizes which freight on rail offers.