Prevention and Management of Road Surface Damage

The UK's road network totals around 250,000 miles of paved roads providing a means for efficient distribution of goods and services, supporting UK economic security and social prosperity, and this support will continue to be needed whatever the future of automated vehicle technology. The entire road network has been valued at £750 billion and as the UK's main transport infrastructure provides a vital service to road users, commerce and industry. However, road surface damage, particularly potholes, has become a serious safety and performance concern for all network users. The need to improve the quality, longevity and accessibility of the highway network is a vital concern of government, industry and the travelling public. It is highlighted by the recent dramatic increase in the number of cars taken in for repair of pothole-induced damage (up from 6.3M to 8.2M in two years according to a Kwik Fit survey, at an estimated annual cost to motorists of about £900M) and the maintenance backlog for local highway authorities, costed at £9.8B by the Asphalt Industry Alliance earlier this year. Episodes of severe weather in recent years (record-breaking rainfall, extreme cold-weather events), combined with tight financial constraints on highway authorities, have also led to a much publicised 'pothole epidemic', and the situation is made worse by the lack of longevity sometimes achieved in defect repairs.

Against this background, this proposal has twin interrelated ambitions to (1) enable the design/construction of roads so as to minimise surface damage (i.e. prevention); and (2) induce a step change in the science of road repair (i.e. management). These ambitions can only be realised by establishing a level of understanding that does not currently exist within the pavement engineering community. This involves isolating, by both experimental studies and theoretical modelling, the real root causes of road surface damage - although it is well known that water and ice play vital roles. This knowledge has then to be combined with evaluation of actual road data in order to produce a robust and validated design and analysis tool and to generate appropriate construction and maintenance guidance. The research needed to successfully deliver these twin ambitions will require the combined effort and expertise of pavement engineers, materials scientists and computational fluid dynamics experts, expertise found at the University of Nottingham and Brunel University. In addition, the project will only be possible through the assistance of industrial partners with specific capabilities that will complement the academic input from Nottingham and Brunel. These comprise: three highway authorities (Highways England, Transport for London and Nottinghamshire County Council), giving access to data resources as well as direct field investigation opportunities; two umbrella organisations (ADEPT - representing local authority highways departments, RSTA - representing suppliers and contractors concerned with road surface treatments); and, finally, one producer of highway material test equipment (Cooper Technology), giving specialist input into test development.

This project will generate an understanding of the mechanisms behind pavement surface damage and skills gained from this project, especially those relating to environmental attack (rain, frost), will be applicable to both pavement engineering and the engineering of other exposed structures. In particular, the project will have significant implication for both specification of surface course materials and damage repair strategies. Specifically, impact will be felt in the following ways:

1) Road authorities (Highways England and local highway authorities) will benefit in the short term by taking advantage of the outcomes of this project to optimise repair design, material selection and repair techniques. They will also benefit in the longer term from the recommendations made for surface course specification, leading to more durable pavement structures. The current £150+ Million cost of UK pothole repairs should fall progressively as changes are implemented, and the durability of both new and repaired road surfaces improves.

2) There will be direct benefit to asphalt material developers, allowing them to target the most effective mixture properties.

3) Improved design capability will also impact on the competitiveness of UK consultants, potentially allowing them to keep one step ahead of the rest of the world.

4) Immediate impact will also be felt by test equipment manufacturers, with the introduction of new and improved testing recommendations.

5) Reducing road surface damage will lead directly to a reduction in operating costs. The proposers' view is that a 1% fuel efficiency gain is realistic in the long term and, since 47.2 billion litres of fuel were consumed by UK road transport in 2017, the saving for the economy would be about £250M per annum (considering only true cost, i.e. excluding tax).

6) It will also lead to fewer injuries and accidents, particularly to cyclists and motorcyclists.

7) The current annual cost of pothole related vehicle repair, currently estimated to be £900M, would be expected to fall dramatically - by over £200M based on recent rates of increase.

8) Increased road user satisfaction would also be expected due to reduced frequency of intrusive and disruptive road maintenance, with time / financial benefit to UK business and the travelling public.