Background to the Study

The Old Military Road (OMR) is a 4.0km road in the south of Argyll and Bute in the Scottish Highlands. The OMR currently serves as a temporary diversion to the A83 Trunk Road, southeast of the Rest and Be Thankful (RaBT), during periods when the A83 Trunk Road is closed.

The RABT is the highest point on the A83 Trunk Road (approximately 265m above ordnance datum), separating Glen Kinglas from Glen Croe. It is also one of the places on the Scottish Trunk Road network with the highest risk of landslides and debris flow hazards, which has increased in recent years due to the frequency of heavy, intense periods of rainfall.

Plan of Glen Croe Southeast of RABT
Figure 1: Plan of Glen Croe Southeast of RABT

As a result, the A83 Trunk Road between Ardgartan and the RaBT car park has been subject of an increased number of closures over the past few years, notably since August 2020. This in turn has put additional pressure on the use of the OMR as the main diversion route. In addition, the OMR itself has had to be closed due to debris flow events above the A83 Trunk Road reaching the OMR, as a result of stream discharges over the OMR and flooding from Croe Water.

The Trunk Road Operating Company, BEAR Scotland, has implemented a number of landslip mitigation measures to improve the resilience of the A83 Trunk Road since 2007 and work continues with ongoing maintenance work at Glen Croe. In early 2021, BEAR Scotland constructed a new temporary 175m long HESCO bund to increase protection on the OMR and is continuing to investigate other measures to improve resilience in the short-term.

Nevertheless, in view of these recent events and potential future works to provide a long-term resilient alternative to the current A83 Trunk Road, consideration is being given to further measures to improve the resilience of the A83 diversion route in the medium-term.

Purpose of this Report

The purpose of this option assessment report is to document the development and assessment of medium-term solution route options, considering the scheme objectives and the engineering, environmental, traffic and economic advantages, disadvantages and constraints associated with each option.

Following this introductory chapter, the remainder of this report is set out within eight chapters, as follows:

  • Chapter 2 Existing Conditions
  • Chapter 3 Objectives
  • Chapter 4 Initial Option Generation and Development
  • Chapter 5 Initial Short Listing
  • Chapter 6 Final Shortlisted Options
  • Chapter 7 Assessment of Final Shortlisted Options
  • Chapter 8 Options Fact Sheets / Key Findings
  • Chapter 9 Conclusion and Recommendation