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

5 Methodology

5.1 Overview

The following approach was adopted for the analyses in this study:

  • Review literature and Transport Scotland information with a focus on areas which, from experience, have most significant impact in terms of network condition, operations and economics;
  • Use results of the literature review to confirm key aspects within the budget levels to be tested for economic impact;
  • Refine the budget scenarios from the overall '20% reduction' and '40% reduction' of the total maintenance and operational budget, based on asset management principles, to arrive at more realistic estimates of budget reductions in key spending categories; and
  • Conduct analyses and report results.

5.2 Focus of the study

There is a wide range of activities included in road operations and maintenance budgets so there were a number of aspects that needed to be assessed in this study to identify the overall economic, environmental and social impacts of changes in levels of maintenance funding. Therefore, for this brief analysis a number of significant assumptions needed to be made. The approach adopted was limited by both the extent of these assumptions and the level of current knowledge of the specific subject area. The key assumptions and parameter values adopted for the analyses in this study are further described in Appendix D.

The general principle adopted was to focus on variations to those activities which either have a significant impact on budget, or a significant impact on economic consequence, or both.

The economic, environmental and social impacts of changes in maintenance funding and, hence, asset condition, were considered in four general areas. First, the possible impacts on travel in terms of potential lost journeys, delayed journeys and the results of these in terms of lost education, working hours etc. Second, the possible impacts on road user safety, in terms of the costs of accidents. Third, the possible impacts on vehicle operating costs in terms of fuel consumption, vehicle maintenance and commercial crew time. Fourth, the potential impacts on carbon emissions. Fifth, the impacts on the residual value of the asset which changes with the amount of funding invested in the asset.

5.3 Analyses and results

Based on the data available, it was not feasible to carry out all the potential economic analyses. The analyses therefore focused on those for which there was sufficient suitable data. The following analyses were carried out:

  • Test impact of different funding levels in terms of long term road surface conditions and the subsequent impact on vehicle operating costs, travel time costs and accident costs;
  • Test impact of different funding levels in terms of changes to pavement operations and the subsequent impact on road user travel time costs due to delays at roadworks;
  • Test impact of different funding levels in terms of other road maintenance and operations (specifically structures, winter maintenance and lighting) and where possible identify any economic impacts;
  • Assess impact on overall asset value and depreciation;
  • Assess the impact on potential feedback from customers; and
  • Translate the identified effects into the impact on the carbon footprint of the road network.

Sections 7 to 12 describe each of these analyses. Section 13 uses the results from the analyses to form an overall view of the economic impact. Section 14 then provides the key conclusions and recommendations.

Note that in Sections 7 to 12, all results which are derived from results of the pavement model analyses undertaken with the Transport Scotland model (i.e. pavement conditions and their impact on vehicle operating costs and travel speeds, roadworks delay costs and carbon footprint) are summarised based on the 3 pavement maintenance budget scenarios.

Section 6 describes how the effect of the Scenarios 2 and 3 budget reductions may lead to a higher cut in the pavement maintenance budget. The results of the analysis of overall 20% and 40% cuts to pavement budgets are therefore factored up in Sections 13 and 14 to reflect the proportionately larger reductions expected when the overall budgets are reduced by 20% or 40% (i.e. Scenarios 2 and 3).

All other analyses in Sections 7 to 12 (for pavement skid resistance conditions, lighting and winter maintenance and operations) are reported based on the estimated reductions to the relevant budgets. Therefore, no further adjustment is needed to these results for the summaries in Sections 13 and 14.