The Scottish Government's Strategic Transport Projects Review identified a number of measures to reduce congestion and improve traffic flows along a number of sections of the A82. 

The route between Tarbet and Inverarnan runs adjacent to the west bank of Loch Lomond for 17 km (10.6 miles).

It is located within the Loch Lomond and The Trossachs National Park in an area of outstanding natural beauty. It is a complex site, physically constrained, with the loch on one side, and the hillside and railway on the other.

The study commission is considering issues including:

  • the impact of widening the road
  • opportunities to improve visibility and reduce the levels of accidents
  • improving drainage
  • pedestrian and cycle access
  • car parking and lay-by provision
  • delivering journey time reliabilityA82 Tarbet to Inverarnan Route Corridor Plan

How to get involved

Transport Scotland and CH2M Fairhurst Joint Venture are working closely with Loch Lomond and The Trossachs National Park, Argyll and Bute Council, Scottish Natural Heritage, Scottish Environment Protection Agency, Network Rail, community councils and others in undertaking the study.

We are also talking to groups representing all users of the A82.

If you would like to register for updates/notifications or if you have any questions please get in touch, you can contact the project team by email at A82upgrade@ch2m.com or alternatively by post to:

A82 Tarbet to Inverarnan
CH2M Fairhurst Joint Venture
95 Bothwell Street
Glasgow, G2 7HX


A drive through video of the stretch of the A82 between Tarbet and Inverarnan can be viewed on YouTube. and a computer generated 3D fly through can also be seen on YouTube.

Community engagement

Engagement with Stakeholders for A82 Tarbet to Inverarnan Scheme

Stakeholder engagement event - 28 March 2018As the design work continues for the A82 Tarbet to Inverarnan scheme, Transport Scotland, supported by its consultants CH2M Fairhurst Joint Venture, hosted an engagement workshop with a wide range of stakeholder organisations in Arrochar on 28 March. 

The workshop set out the developing route alignment and sought feedback from those attending on the design and assessment work carried out to date. 

The workshop also provided an opportunity for the project team to understand the views of the stakeholder groups and to consider some of the opportunities and options that will inform the developing route alignment as we look to prepare draft Orders for the scheme later this year.


A82 Tarbet to Inverarnan Public Exhibition

Public exhibitions were held between 30 September and 6 October 2015 at Arrochar, Crianlarich, Oban and Fort William.

They gave the public an opportunity to view the preferred option and to discuss the assessment work with members of the Transport Scotland and CH2M Fairhurst project team.

DMRB Assessment Process

The design and assessment of Trunk Road schemes is guided by the Design Manual for Roads and Bridges (DMRB). This involves a 3 stage assessment process, examining and assessing a number of options leading towards the identification of the preferred alignment at the end of DMRB Stage 3.

Following the identification of the preferred corridor, alternative routes within this corridor were examined during DMRB Stage 2. Assessment work was concluded in September 2015 with the selection of the online upgrade as the preferred route option.

At the end of DMRB Stage 2 public exhibitions were held at Arrochar,  Crianlarich, Oban and Fort William. They gave an overview of the route option assessment work Transport Scotland has taken forward for the A82 Tarbet to Inverarnan upgrade project and presented the preferred route option.

At DMRB Stage 1, a number of transport planning objectives were set and a preferred route corridor was identified.

DMRB Stage 3 Assessment - Preferred Route Development

We're currently taking forward the development and assessment of the preferred route option through DMRB Stage 3.

This stage of the assessment process includes:

  • Development of the scheme design;
  • Consultation with stakeholders, affected landowners and the general public;
  • Development of suitable mitigation measures to reduce impacts on the environment;
  • Environmental impact assessment of the scheme design and preparation of the Environmental Impact Assessment Report;
  • Identification of the land required for the scheme and preparation of Draft Orders in the coming months.

Carriageway Width Review

Tree climbing bat surveysThe DMRB Stage 2 assessment recommended consideration of both a 6m and 7.3m carriageway width (both with 1.0 metre hardstrips) during Stage 3. The assessment of these options was completed in June 2017 with the ministerial announcement that the 7.3m wide carriageway option had been selected.


A number of surveys have been carried out to date to inform the assessment and development of the preferred route option. These have included:

  • Topographic and bathymetric surveys
  • Seasonal ecology surveys (including bats, otters, birds and bryophytes)
  • Noise assessments
  • Vegetation surveys
  • Traffic surveys
  • Woodland and invasive plant surveys
  • Mapping of both major and minor watercourses
  • Peat probing at a number of selected locations along the route, with samples taken for testing.

DMRB Stage 3 Geotechnical Investigation

Ground investigation worksDetailed ground investigation works were carried out along the proposed A82 route corridor over the course of Spring/Summer 2018 and consisted of drilling of land and overwater exploratory holes.

The ground investigation has provided vital information on the challenging ground conditions and geology of the site and is currently being used to inform the detailed development and assessment of the preferred route option.

DMRB Stage 2 Assessment - Preferred Route Identification

Design, assessment and survey work for the DMRB Stage 2 Assessment was completed in September 2015 with the identification of a preferred route option. The work looked at a range of issues, including:

  • environmental impact
  • ground investigation
  • traffic impact
  • economic assessment
  • value for money

The study followed an objective led approach informed by consideration of the problems and constraints.

A number of route options and sub options were considered and sifted. Four route options were then developed for assessment as follows:

  • Route Option 1 – an online route
  • Route Option 2 – an online route with inland sections
  • Route Option 3 – an online route with over-loch sections
  • Route Option 4 – an option with fewest bends

Based on the route options assessment process, Route Option 1 – online upgrade – was identified to be taken forward as the preferred route option. Further consideration is also to be given to the following, as part of the design and development of the preferred route option (DMRB Stage 3 assessment process):

  • Inclusion of two short off-line sections near Ardvorlich
  • The alignment will be developed to reduce impact on properties and landowners
  • The alignment will also be adjusted to assist construction and reduce delays to road users
  • A carriageway width of 6 metres and 7.3 metres (both with 1 metre hardstrips) will be considered

Computer generated fly through of the indicative prefer route

DMRB Stage 1 Assessment - Route Corridor Assessment

The Design Manual for Roads and Bridges (DMRB) Stage 1 assessment to identify a preferred corridor agreed specific Transport Planning Objectives (TPO) that best defined what the scheme is trying to achieve.

The five TPOs developed were:

  1. To improve journey times for A82 trunk road users between Tarbet and Inverarnan (based on observed post Pulpit Rock scheme).
  2. To reduce personal injury accident numbers and their severity on the A82 between Tarbet and Inverarnan to be closer to or better than national KSI (Killed or Seriously Injured) rates.
  3. To provide appropriate stopping opportunities for visitors and for all trunk road users on the A82 between Tarbet and Inverarnan taking account of the unique setting of the route within the National Park.
  4. To seek to provide opportunities for enhanced access by sustainable modes of travel along the A82 corridor between Tarbet and Inverarnan.
  5. To reduce disruption to road users resulting from the undertaking of maintenance activities on the A82 between Tarbet and Inverarnan.

A82 Tarbet to Inverarnan route optionsA wide range of route corridors were identified and following an initial sifting process using the above objectives, the three most feasible route corridors were narrowed down to:

  • Route Corridor 1 - the existing A82 route corridor
  • Route Corridor 2 - a route corridor from Arrochar to Inveruglas along Glen Loin to where it joins the existing A82 route corridor
  • Route Corridor 3 - a route corridor above and to the west of the West Highland Rail line

An assessment of the engineering challenges, environmental effects and traffic and economics concluded that Route Option 1 (A82 on-line, the ‘red route’ - see plan above) was the preferred corridor.

Other options, such as a straight line tunnel through the hillside or a submerged tunnel in the loch were also considered, but sifted out at an early stage because they failed to meet all of the objectives. It is also notable that the £4 billion estimated cost of the tunnels was considerably higher and would have provided a significantly lower economic return than the other options.

The project advanced to DMRB Stage 2, with the assessment and identification of a preferred route within the corridor.