Economic, Environmental and Social Impacts of Changes in Maintenance Spend on the Scottish Trunk Road Network

1 Introduction

The road network in Scotland is the largest and most valuable community asset in Scotland and the trunk roads comprise the strategic routes that play a key role in the economic performance of Scotland.

In 2011, Audit Scotland highlighted that the overall maintenance backlog on the roads in Scotland was £2.25 billion of which approximately a third related to the trunk road network (Audit Scotland, 2011). The report included a central recommendation for the Scottish Government to take forward a national review of "how the road network is managed and maintained, with a view to stimulating service redesign and increasing the pace of examining the potential for shared services."

In response to this report, The Scottish Government set up a National Road Maintenance Review to look at how the trunk road and local road networks in Scotland are managed and maintained.

The Review was taken forward by Transport Scotland in partnership with the Convention of Scottish Local Authorities (CoSLA), the Society of Local Authority Chief Executives (SOLACE), Society of Chief Officers of Transportation in Scotland (SCOTS) and the Scottish Road Works Commissioner under the guidance of a Steering Group. The Steering Group was supported by four Working Groups drawn from Steering Group member organisations as well as invited stakeholders. This study and an associated study for local roads were commissioned to provide evidence of the effects of different levels of road maintenance funding for the Wider Economic Issues, Impacts, Costs and Benefits Working Group (WG4).

The aim of the study was to investigate the effects of changes in road maintenance funding between 2010 and 2030. Three scenarios have been considered in the study:

  • Scenario 1 (Base case): Constant annual level of maintenance spend (2010/11 funding level continues) for 20 years
  • Scenario 2: Reduction in the annual maintenance spend in Scenario 1 by 20% (starting 2010/11) for the first 10 years. Return the annual spend to current 2010/11 levels using annual uniform increases, between 2020 and 2025. From 2026, increase annual funding by 2.5% per year
  • Scenario 3: Reduction in the annual maintenance spend in Scenario 1 by 40% (starting 2010/11) for the first 10 years. Return the maintenance budget to current 2010/11 levels using annual uniform increases, between 2020 and 2025. From 2026, increase annual funding by 2.5% per year

Transport Scotland has described a wide range of possible impacts that may be considered as part of the review. These cover all aspects of maintenance and operations spend. The study considered the current internationally available evidence, analysed potential changes in the amount of maintenance undertaken on the trunk road network and where possible estimated the changes in overall costs. Changes in cost arise from various aspects and this study has assessed:

  • Changes in Transport Scotland maintenance budgets and asset values;
  • Changes in accident rates;
  • Vehicle operating costs and vehicle depreciation;
  • Changes in journey time;
  • Global (i.e. CO2) emissions; and
  • Customer satisfaction.

Inevitably there are interactions between these effects that will affect the overall impacts caused by changes in maintenance funding. For the purposes of this study each effect was considered independently.

The effects of the different levels of pavement maintenance funding were based on the predicted pavement condition from the Transport Scotland Pavement Network Model. For the study, using data from the Transport Scotland asset database, the model was used to predict the network condition for 2013, 2017, 2020, 2025 and 2030 for each funding Scenario. The effects on network condition in intervening years were derived by interpolation. The model expresses pavement condition as the Road Condition Index (RCI). To use the outputs from the model in other analyses (e.g. vehicle operating costs in HDM-4 (Watanatada, Harral, Paterson, Dhareshwar, Bhandari, & Tsunokawa, 1987) and studies on the effect on traffic of deteriorating pavement condition) RCI values were converted into International Roughness Index (IRI) and 3m Longitudinal Profile Variance.

In line with the Scottish Transport Appraisal Guidance (STAG) (Transport Scotland, 2011b) (Transport Scotland, 2011b) (Transport Scotland, 2011b)requirements, the results of all the analyses given in this report are given in 2002 prices to enable comparison with different studies over time. Real increases were assumed for the costs of vehicle fuel and road user time in line with this guidance, consistent with standard UK guidance (Transport Scotland, 2011b) (Transport Scotland, 2011b) and (Department for Transport, 2011), costs of maintenance works and carbon emissions. The effects of discounting all future costs at the annual Treasury Test Discount Rate were considered. The analyses included an estimate of traffic growth during the analysis period. As part of the analysis of the impacts on local roads (Transport Scotland, 2012), the sensitivity of the results to real changes in maintenance works costs was examined.

Little information was available for non-pavement assets. Although it was expected that some maintenance reductions would be applied in the technology areas (e.g. signs and ITS), the effects of those reductions have not been quantified in this study.

For this analysis, the portion of the network managed as DBFO concessions has been excluded. The study describes the potential effects of reducing the maintenance budget on the part of the network managed directly by Transport Scotland with no changes to the DBFO concession agreements.

The report:

  • Describes the results from available literature covering the aspects of the study;
  • Summarises the information available on the current status and operation of the network; and
  • Explains the approach adopted for, and the results of, each of the relevant analyses that have been carried out into the effects of changes in the level of maintenance funding.

The associated study for local roads (Transport Scotland, 2012) has provided the same sorts of information to the National Road Maintenance Review and a Summary Report (Transport Scotland, 2011a)(Transport Scotland, 2011a) combines the results from this report and the local road study to provide an overview of the impact for the entire Scottish road network.