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

Executive summary

This report summarises the results of a study to assess the economic, environmental and social impacts of cuts to the roads maintenance budgets for trunk roads in Scotland. It describes the methodologies adopted, presents the results from the analyses and discusses the conclusions from the results. This study and the associated study for the assessment of impacts of reductions in maintenance funding for local roads in Scotland provided evidence for the National Road Maintenance Review for Scotland conducted by the Scottish Government initiated in 2011.

The study showed that the economic and social disbenefits to Scotland are greater than the savings in maintenance budgets. The net effects of the reduced budgets were decreases in economic welfare of £107m and £78m (Net Present Value at 2002 prices) for the overall maintenance funding reductions of 20% and 40% respectively.

This study examined the effects of different levels of maintenance funding for the Transport Scotland trunk road network, excluding the portion of the network managed as DBFO concessions, between 2010 and 2030. A brief literature review was undertaken to identify and incorporate similar analyses into this study but a fuller literature review was undertaken in the study for local roads. The study for local roads also included some sensitivity analyses that were applicable for both trunk and local roads.

Three funding scenarios were considered in the study. These all considered constant levels of spend through the first 10 years of the period. The first assumed the spending level in 2009/10 continued and the other scenarios assumed the 2009/10 level of funding was reduced by 20 percent and 40 percent. The first scenario assumed the constant (2009/10) funding also continued for the last 10 years of the analysis period. For the two scenarios with reduced funding, during years 10 to 15 of the analysis period, the funding was restored uniformly to the 2009/10 level and from years 15 to 20, the funding was assumed to increase by 2.5% per year. The results of all the analyses are shown at 2002 prices. The study examined the amount of maintenance undertaken on the road network, assuming standard national growth rates in traffic flow, and assessed the impacts of reducing the current funding in terms of changes in network condition, accident rates, vehicle operating costs, vehicle depreciation, road user journey time, global (i.e. CO₂) emissions and customer satisfaction.

Changes in the level of overall maintenance funding were specified but it was recognised that the overall reductions may not affect all aspects of maintenance equally. A subjective assessment was made of the likely distribution of the overall budget reductions across Transport Scotland maintenance activities. From this analysis it was clear that in the period considered in this study it is likely that pavement maintenance will suffer a bigger share of the budget reduction than other maintenance areas. An investigation into the likely effects on different maintenance activities suggested the pavement maintenance budget would be reduced by 44% and 76% for reductions in the overall maintenance budgets of 20 percent and 40 percent respectively.

The budget reduction scenarios mean undiscounted pavement maintenance funding reductions over 20 years of £304m and £674m (£266m and £568m discounted back to the base year) for the overall 20 percent and 40 percent budget reductions respectively.

For the analyses used in this study, during the first 10 years of the analysis period, maintenance on Motorways was given a higher priority than maintenance on the All Purpose Trunk Roads. Using this strategy the condition of Motorways continued to improve for all the budget levels considered but overall there is a worsening in network pavement condition and with Scenario 3 (40% cut in the overall maintenance budget) the percentage of the network with zero remaining life (i.e. in need of maintenance) was predicted to be 25 percent of the network by 2020 and 29 percent by 2030, compared with 11 percent in 2010.

The ISOHDM model, HDM-4, was used to assess the effects on vehicle operating costs, including vehicle depreciation, of changes in network condition resulting from the reduction in maintenance funding. Using typical UK vehicle types in HDM-4, it was estimated that in 2030 there will be an increase in undiscounted vehicle operating costs of approximately £1,200m per year compared with the current level, for the scenario which retains the current level of maintenance spend (i.e. Scenario 1). The results of the analyses show there will be bigger increases following cuts in the maintenance budget. With a 40 percent overall budget reduction the vehicle operating costs were predicted to be £1,241m per year more in 2030 than the costs in 2010.

Using the results of a brief study carried out some years ago into the effects of pavement condition on traffic speed, the annual undiscounted costs of increased travel time, by 2030, resulting from the worsening in pavement condition, were estimated to be £7m, £13m and £17m for the constant level of spend, 20 percent and 40 percent budget reduction scenarios respectively.

A sample of typical maintenance works was used with QUADRO analyses to assess the impacts on road users from changes in the number of maintenance schemes with the reduced maintenance funding. The results show a reduction in the undiscounted costs of traffic delays to road users at roadworks of £2m per year, compared with the 2010 level, for all three funding scenarios considered.

For this study, it was considered that safety would continue to have a high priority with reduced maintenance budgets, but carriageway condition would still deteriorate due to the lower maintenance funding and this was predicted to lead to lower levels of skid resistance. The increase in accidents that accompanies lower skid resistance was expected to become significant with a 40 percent cut in the maintenance budget and this would lead to increased costs of more than £4m per year by 2020 but reduce back to the 2010 level as the funding increases in 10 years up to 2030.

With the importance to Transport Scotland of road safety, it was recognised that funding of winter maintenance would remain a high priority even at the lowest funding level considered (i.e. only a small budget reduction would be applied to winter maintenance if the overall budget is reduced by 40 percent). This study did not therefore include any prediction of the change in accident rates that may arise from a change in the level of funding of winter maintenance. Other studies have considered the overall disruption caused by inadequate levels of winter maintenance but it was not possible, in this study, to reliably predict any effect on the total road user travel time that may result from changes in levels of winter maintenance due to cuts in the overall maintenance budget.

For structures, a Transport Scotland study in 2010 examined the effects of changes in the level of maintenance funding. The budget reductions in that study (the biggest reduction was 15 percent) were less than the overall cuts examined in this study but represented the likely effect on structures maintenance following the subjective review of the current maintenance budget. This reduction in funding was not expected to lead to bridge closures but would increase the amount of routine maintenance required in the absence of the renewals maintenance and may introduce difficulties for the 4 Operating Companies in future years. The effect on road users of this change in funding was not assessed as it was expected the reductions would have only a small impact.

Maintenance operations contribute to the carbon footprint of the road network in a number of ways. This study considered the changes in levels of carbon dioxide emissions from production and use of asphalt materials, the disruption to road users caused by road maintenance and the CO₂ from changes in fuel consumption on rougher pavement surfaces. The analysis showed a predicted increase in the undiscounted costs of carbon emissions of £139m per year in 2030 if the current level of maintenance funding is retained. With the 20 percent and 40 percent cuts in maintenance funding, that increase was predicted to be reduced by £3m and £15m respectively.

The effect of maintenance budget reductions for street lighting was examined by comparing the reduced energy costs and the increase in the number of traffic accidents that may result from lower lighting levels. The overall savings identified were small but it was recognised that bigger savings may be possible at specific locations. The overall increase in undiscounted total accident cost was estimated to be £2.0m over the analysis period for savings in the Transport Scotland energy bill of £12m (for Scenario 3, the 40% reduction in the overall maintenance budget).

Studies by Transport Scotland since 2008 of road user perceptions of trunk roads in Scotland showed that the condition of the road surface is a general concern for road users. It is therefore expected that, with the predicted worsening in network condition, users will continue to have the same level or more concern about pavement condition.

The study showed that with the overall deterioration in network condition the undiscounted total non-works costs were predicted to increase by approximately £1,336m per year by 2030 for each of the three funding scenarios. Over the analysis period, the discounted non-works cost for the 20 percent funding reduction scenario was predicted to be £107m less than the scenario with constant maintenance funding but £80b less for the 40 percent funding reduction. The overall increases in undiscounted non-works costs, over the constant level of funding scenario, were predicted to be £569m and £986m for the 20 percent and 40 percent overall maintenance funding reduction scenarios respectively. The increases in discounted costs were £373m and £647m for the two Scenarios respectively. Those increases exceeded the savings to Transport Scotland from reduced maintenance costs over the analysis period so the net effect is an increase in the total transport cost with reduced maintenance budgets.

For the two funding reduction Scenarios, the biggest change in non-works costs relative to the base case was in vehicle operating costs due to changes in road surface condition. In year 2030 the undiscounted overall non-works costs were predicted to be £154m higher for the Scenario with a 40% overall reduction in the maintenance budget, than for the Scenario with the current level of maintenance funding.

Using results from the Transport Scotland asset valuation model to estimate the value of the trunk road network and the year on year depreciation of the asset, the effects on the road network asset value caused by the different levels of maintenance funding showed the worsening condition would be reflected in a lower asset value by 2030. At the end of the analysis period, compared to the value when the 2010 level of spend is retained, there was little change in the asset value with the 20 percent reduction in maintenance funding and a reduction of £44m in the undiscounted asset value for the 40 percent funding reduction. With a 40 percent reduction, the decrease in undiscounted asset value in 2030, compared to 2010, was predicted to be more than £530m.