The A9 dualling project – crucial for Scotland?

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The Scottish Government is committed to dualling the 80 miles of single carriageway A9 trunk road between Perth and Inverness at a cost of £3 billion.  Scottish Ministers have recently been questioned about the compatibility of this project with the Infrastructure Commission recommendation that there is no net increase in road space for private vehicles and legally binding Scottish greenhouse gas emission reduction targets.  In response, Ministers have argued that the project is crucial to the economies of the Highlands and Perthshire while also improving road safety.

This blog, which builds on an earlier post on the Scottish Budget for 2020-21, outlines the predicted economic and road safety benefits of dualling the A9 between Perth and Inverness.

Economic Benefits

The expected costs and benefits of dualling the A9 are set out in the A9 Dualling Case for Investment, published by Transport Scotland in September 2016.

The project appraisal covers a period of 60 years, which is standard for major transport projects, and uses 2010 prices. It concludes that the direct benefits of the project, which includes journey time savings, lower vehicle operating costs and road safety benefits offset against the negative environmental impacts, are £419 million less than the cost to the Scottish Government.  This means that the project would return 78 pence in benefits for every pound spent by the Scottish Government.

However, the project would also produce Wider Economic Benefits (WEBs) – which is a specific term in transport appraisal.  The WEBs of the A9 dualling project were assessed under three broad headings:

  1. Agglomeration: This describes any likely increases in productivity or reductions in costs due to people and businesses grouping together in a way that offers economies of scale.
  2. Imperfect competition: This measure accounts for lower prices and increased economic output due to the creation of more competitive markets.
  3. Labour supply: This measure accounts for additional tax income to the Government from people who have entered the labour market because of improved accessibility to employment opportunities.

The WEBs of the A9 dualling project were calculated as £210.4 million.  Taking these into account, the project would return 89 pence in benefits for every pound spent by the Scottish Government.

In addition to WEBs, the Case for Investment highlights opinion research conducted with businesses located near the route of A9 which “…indicated that increased attractiveness of the area for investment, reduced transport costs and improved business confidence were the principal benefits of dualling the A9.”

This would usually represent the conclusion of the transport appraisal process.  However, the Scottish Government commissioned consultants to develop a method for placing a monetary value on “removing driver frustration” as part of the A9 dualling project.  This is separate from, and additional to, the monetary values already calculated for reduced journey times and collisions.  The figures used in these calculations are not publicly available, although information on the method is available in a conference paper produced by the researchers.

The value of removing driver frustration is assessed as £430 million – £86 million more than the value given to collision reduction.  Once the value assigned to removing driver frustration is added, the project would return £1.12 for every pound spent by the Scottish Government.

The detailed guidance for those involved in assessing Scottish transport projects, Scottish Transport Appraisal Guidance (STAG), was updated in January 2015 to include reference to this new method.  However, based on publicly available information, the A9 dualling project appears to be the only scheme to date where this method has been used as part of the detailed project appraisal process.

It is worth noting that, prior to this update to STAG technical guidance, the Scottish Planning Policy (June 2014, page 62) had introduced the concept of a transport hierarchy into national policy.  This policy most recently featured in the new National Transport Strategy, published on 5 February 2020, which states that “…we will embed the Sustainable Travel Hierarchy in decision making by promoting walking, wheeling, cycling, public transport and shared transport options in preference to single occupancy private car use for the movement of people”.

Sustainable transport hierarchy

Road safety benefits

The statistical risk of a crash resulting in death or serious injury occurring on Britain’s strategic road networks, for the period 2015-2017, is set out in the British EuroRAP Results 2019 report (EuroRAP is the European Roads Assessment Programme).  The risk is calculated by comparing the frequency of road crashes resulting in death and serious injury on every stretch of road with the volume of traffic carried. Risk is reported using a five-point scale.  The A9 between Inverness and Dalwhinnie is currently rated as Low Risk (the safest category) while the section between Dalwhinnie and Perth is rated as Low-Medium risk (the second safest category).

Transport Scotland assessments indicate that the A9 dualling project will produce a significant reduction in fatalities, a slight decrease in serious injuries and an increase in slight injuries and damage only collisions, as set out in the table below.

Predicted increase/decrease in people killed or injured (by severity) and damage only collisions in selected years following the completion of the A9 dualling project




Damage Only











However, this is based on data produced before two significant road safety interventions had been implemented on the A9 between Perth and Inverness, both of which began on 28 October 2014. These are:

  • HGV speed limit increase: The speed limit for goods vehicles weighing over 7.5 tonnes on single carriageway sections of the A9 was increased from 40mph to 50mph. The assessment of the first three years of the higher limit concluded that vehicle speeds were more consistent, the average difference in speeds between HGVs and other vehicles had reduced, there were fewer slow moving HGV-led vehicle platoons and drivers were less frustrated.
  • Average speed cameras: The impact of average speed cameras on the single carriageway sections of the A9 between Perth and Inverness was assessed after three years. This found that, compared with the three years before cameras were installed, annual average fatalities were down by 40%, total casualties were down by 27% and the average number of collisions were down by over 23%.  In addition, there had been a 25% fall in the time the road was closed/restricted due to collisions.  There had been a 13% increase in annual average traffic volumes between the 2013 baseline and 2017.

In the three years following the installation of average speed cameras and the increase in the HGV speed limit, annual average fatalities on the A9 between Perth and Inverness fell from seven to four – when compared with the average of the preceding three years.

Alan Rehfisch, Senior Researcher, Transport and Planning