Economic, Environmental and Social Impacts of Changes in Maintenance Spend on the Scottish Trunk Road Network
9 Impacts of other maintenance operations
As noted in Section 2, there has been much less quantitative reporting on the economic impacts from budget reductions for non-pavement operations. This part of the study has focused on three key areas of budget spend and potential impact:
- Structures maintenance;
- Winter maintenance; and
- Street lighting.
9.2 Major structures and impact on the road user
Spend on major structures represents a significant proportion of the Transport Scotland budgets (£26m for 2010/11). The issues surrounding structural maintenance of structures which differentiate the asset group from the other road assets are:
- Design/economic lives. Design lives of major structures are significantly longer than the lives achieved for other assets and it is not uncommon for structures to be in service well beyond the original predicted design lives. Tools for the prediction of the impact of variation in year on year maintenance budgets are much less developed than for pavements and forecasts of the effects of future maintenance budgets are less reliable.
- Risk. The risk associated with structures can be significant. If structures are found to be unsafe, there is a significant potential impact in terms of both accidents and route availability which is significantly higher than the impact from most other assets.
- Cost per unit of asset. Major structures, when they do require maintenance, often require very significant amounts of investment and combined with the issues of risk and design life, this can lead to large changes to maintenance budgets, sometimes at short notice, when defects are identified.
Section 4.2 summarised an assessment by Transport Scotland of the effects of potential future structures maintenance budgets. The assessment provided subjective comments on the economic impacts of the assumed budgets, but no quantitative economic analysis had been undertaken.
The nature of trafficking the network with or without the availability of structures is very specific to the routes containing those structures. It is therefore much less appropriate to scale up generic conclusions on the effects of maintenance budget changes seen on other networks. Any analysis of the effects of maintenance budget changes on the structures stock on the Scottish trunk road network would need analysis to include elements of risk assessment and specific technical analyses of the structures most at risk.
Development of tools, or the use of existing tools, to undertake such an analysis was beyond the scope of this study.
9.3 Winter maintenance and travel delay and accident costs
9.3.1 Literature review
There have been limited studies into quantifying the economic benefits of winter road maintenance under specific weather conditions. Such studies have tended to assume uniform road and weather conditions regardless of local variables, which can introduce particular consequences, apart from any changes in winter maintenance policy and funding levels. Inevitably, any realistic forecast of the effects of winter maintenance funding is dependent on reliable forecasts of the future weather conditions on the network. Studies into the effects on journey time are particularly unreliable while studies into the effects of winter maintenance on the number of accidents may be more relevant.
An American study (Hanbali & Kuemmel, 1992) concluded that significant reductions in accidents were observed after salt/salt-abrasive mixes had been spread. The average reduction in accident rates was 87% and 78% for two lane single carriageways and dual carriageways, respectively.
A study in 2006, (Fu, Perchanok, Moreno, & Shah, 2006) investigated the relationship between road safety in Canada and various weather and maintenance factors, including air temperature, total precipitation, and the type and amount of maintenance operations. They concluded that anti-icing, pre-wet salting with ploughing and sanding have statistically significant effects on reducing the number of accidents. Both temperature and precipitation were found to have a significant effect on the number of crashes. However, later research (Usmana, Fua, & Miranda-Morenob, 2010) has pointed out limitations which mean the earlier (Fu, Perchanok, Moreno, & Shah, 2006) research may not be directly applicable for quantifying the safety benefit of winter road maintenance of other highways or maintenance routes.
Nordic countries have conducted extensive research on issues related to winter road safety and road maintenance (Wallman, Wretling, & Oberg, 1997). The findings in general are consistent, showing that winter weather increases the risk of accidents and that application of winter maintenance measures lowers the accident risk. Another Nordic study showed that winter maintenance activity is not enough to maintain traffic safety completely and that other actions, such as increasing driver awareness of slipperiness hazards, are required in combination.
The Winter Resilience Review for the Department for Transport (Quarmby, Smith, & Green, 2010) looked at the economic benefits of winter maintenance in terms of:
- Lost economic output if people cannot get to work;
- Personal time lost due to travel delays and lost journeys;
- Additional road vehicle collisions; and
- Personal and health service costs of slips, trips and falls causing personal injury.
The analysis showed on average there was an annual benefit of around £1 billion from adequate winter maintenance funding during a 'hard' winter in England. The cost to highway authorities in England of providing winter service has been estimated to be around £160 million per year. However, the study did not include any further information on impacts of any incremental changes to budgets.
In summary, the literary evidence supports a strong case for investing in winter maintenance both economically and socially, with a significantly positive cost-benefit ratio on the side of 'benefit'. This supports the approach taken in the subjective assessment described in Section 6 and Appendix B in which the spend on winter maintenance was to a large degree protected in the budget reductions.
9.3.2 Winter maintenance assessment
22.214.171.124 Safety impact
This study has assessed the order of magnitude of the impact of potential budget reductions on road accidents in winter on the Scottish trunk road network.
It was assumed that the number of accidents in winter is greater than in summer due to poorer light conditions and more unsafe surface conditions due to water, snow and ice. The data provided by Transport Scotland for a Swedish study, which showed the variation in accidents during last 5 years by winter/summer, suggested around:
- 30 more fatal accidents per year in winter than in summer
- 500 more accidents of any severity per year in winter than in summer
At typical UK accident cost rates, this puts the value at between £35m and £50m per year.
The current winter maintenance funding allocation for trunk roads by Transport Scotland is around £8m per year. Given that winter maintenance has such an important impact on road safety and journey reliability, the subjective assessment in Section 6 supports this and shows that the budgets would be 97% and 89% of the existing winter budgets, for the funding Scenarios 2 and 3 respectively.
For this study, the information and analysis tools could not quantify any impact at the 97% or 89% funding level so the impacts from Scenarios 2 and 3 are uncertain. Whilst the risk of accidents might go up with reduced winter maintenance, the amount of travel will reduce if fewer roads are kept open, so that this in turn will potentially reduce the number of accidents.
It has therefore been concluded that it is not possible to reliably quantify the safety impact of variations to winter maintenance activities for the levels of overall budget reduction considered in this study.
126.96.36.199 Travel time impact
The Winter Resilience Review (Quarmby, Smith, & Green, 2010) concluded that the major economic impact of lack of winter maintenance is in terms of lost trips and extended travel time. It was recognised that salting and gritting budgets lead directly to the availability of the network, in so far as every tonne of salt for a given length of road could keep that length of road open for a given length of time under assumed conditions. Any reduction in the salting budgets could therefore directly translate into a reduction in the number of day-km that the roads are kept free of ice. The effects the reduced salting has on vehicle speeds is again subject to levels of traffic flow, time of day and prevailing weather conditions.
However, as for the safety analysis in Section 188.8.131.52, given that the scenarios considered in this study include reductions to the winter maintenance budget of only 11% in the worst case (Scenario 3), and even this would probably be subject to considerable internal debate and political pressure, no further analysis has been progressed.
184.108.40.206 Analysis results
The overall conclusion is that winter maintenance variation will be limited for either of the analysis scenarios, so there will be no resulting economic impact to consider in this study.
9.4 Lighting operations, travel time and accident costs
9.4.1 Literature review
Recent research on lighting costs, technologies and accident statistics has started to change attitudes and assumptions about changes in lighting policies. As well as any economic efficiency drivers, the reduction of lighting energy use is also required by a number of related EU Directives and Statutory Instruments such as the CRC Energy Efficiency Scheme (first sales of allowances was due to be held in April 2011), Energy Related Products Directive (requiring the environmental performance of products throughout their life-cycle to be considered), and the Green Public Procurement Directive.
A TRL study in 2005, (Crabb, Beaumont, Steele, Darley, & Burtwell, 2005), found that the visibility of a small target and reaction times to peripheral objects were not significantly altered either by switching to white light or by a reduction in luminance (by electronic dimming) from full to half the luminous output for Ceramic Metal Halide (CMH) or High pressure Sodium (HPS) lights. This supports later research that has questioned the global applicability of the traditional 30% accident reduction figure used to justify the introduction of night-time lighting on a stretch of road (Crabb, Crinson, Beaumont, & Walter, 2009). As a result of this and other research, the Highways Agency in England now recommends the use of a figure of 10% for the reduction in the number of accidents when calculating the cost-benefit ratio for lighting on the English trunk road network.
The TRL cost analyses (Crabb, Beaumont, Steele, Darley, & Burtwell, 2005) showed that a 22% energy saving can be achieved though the adoption of a dimming strategy. This requires the use of white light (utilisation of lower wattage lamps) and dimming to half the full light output for half of lighting hours at time of low traffic flow. Later, it was also shown (Crabb, Beaumont, & Webster, 2009) that switching from HPS lighting to CMH provides an improvement factor (in energy use) of 1.8.
In Street Lighting - Invest to Save (Institution of Lighting Engineers, 2006) it was suggested that the indirect benefits of street lighting are more than the direct cost of powering the lights and suitable alternatives can be used to reduce energy costs. The use of lower switch on/off lighting levels for some lamp types can save up to the equivalent of a month's energy requirement (per lamp) every 4 years (i.e. around 2%). Reduced traffic route lighting can also provide significant savings. There is also reinforced support for the use of "white light" (lamps with a colour rendering index greater than 60).
In order to implement new strategies, such as dimming, the current infrastructure may require adaptation. In a further TRL study, (Crabb, Beaumont, & Webster, 2009) it was shown that the cost of new elements required to upgrade to controllable lamps was balanced by the saving in electricity in a 30 year whole life cost analysis. It was further commented that as the electricity price increases, the return would be achieved in a shorter period.
In 2011, Local Highway Authorities trialled part-night lighting schemes (e.g. Leicestershire, Gloucestershire, Wokingham, Essex, Devon) and the Institute of Lighting Engineers has issued a briefing note for decision-makers with responsibility for public realm lighting (Institution of Lighting Engineers, 2010) recommending that street lighting should not be turned off. The recommendations also included the consideration of dropping a lighting class, changing to 'white light' (e.g. BS5489 (British Standards Institution, 2003)) allows a drop of one lighting S class by using white light), adopting new technology (electronic control gear replacing old magnetic gear can immediately save 10% of energy, or the use of LED lighting), dimming of lighting on traffic routes when traffic flow is low, retaining lighting uniformity (i.e. not switching off alternate lamps), and switching off lights in rural locations only after all parties have been consulted and the majority agree with the proposed curfew times.
9.4.2 Lighting the network
Based on the results described in the available literature, a simple approach of assuming that should a 100% reduction in street lighting ever be implemented (i.e. turning off all electricity to all lights), then the accident rate on lit routes would increase by 10% (using the current Highways Agency cost-benefit recommendation in reverse). A subjective assessment as part of this study suggests that for a 20% total budget cut (Scenario 2), electricity charges would be reduced by 15% and at the 40% reduction in the total maintenance budget (Scenario 3), the charges would be reduced by 35%, from the current £3.3m per year for the Scottish trunk road network.
Using the accident statistics from the asset database and filtered by those accidents occurring on sections of lit road between 2005 and 2009 inclusive, the average number of all accidents on those roads was 141 and 2.2 of these were fatal.
Assuming a 10% increase in accidents on those roads where lights would be switched off, and assuming that the accidents and electricity charges are equally distributed across the street lighting asset, this equates to a potential economic disbenefit of £0.1m per year with the Scenario 2 funding reduction (with savings in the Transport Scotland energy costs of £0.5m per year) or £0.2m per year with the Scenario 3 funding reduction (with savings in the Transport Scotland energy costs of £1.1m per year).
It was recognised that this could be a significant underestimate of the disbenefit, as the 10% figure recommended for use by the Highways Agency is based on new schemes to be considered now and the benefits are probably less clear than those provided by some of the existing sites where street lights are already in place. However, if the earlier 30% figure is used this would still only produce a disbenefit of between £0.75m and £1.5m per year (i.e. similar to the saving in the Transport Scotland street lighting energy costs).
9.5 Analysis results
The review suggests further work could usefully assess the increased risk to structures of changes in maintenance budget levels. However, because cuts in maintenance of structures and many of the other non-pavement maintenance operations have such a significant impact on road safety, it is likely that if cuts to the maintenance budget are needed these would be aimed primarily at pavement maintenance, as assumed in the subjective assessment (Section 6).
Closer monitoring of structures may enable the structures budget to be better targeted but this is unlikely to lead to significant savings and there would be a strong aim to maintain structures to prevent any bridge closures. For the trunk road network, the traffic delay costs that would result from any such closures are likely to out-weigh the short term maintenance savings.
Some savings may be possible on winter maintenance but climate is the main determinant of the amount of money spent on this aspect of maintenance. It is not a reliable position to expect year on year savings from winter maintenance as a bad winter would upset the budget planning process. Spend on winter maintenance was preserved in the subjective analysis described in Section 6.
Street lighting offers the potential for some savings but the overall impact is unclear when accidents and other related benefits (e.g. security) are included in the analysis. There is not a large scope for maintenance savings in this area but bigger savings may be made at specific locations.
Overall, the increase in undiscounted accident costs could 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).