The proposed project will :
- study the likely differences in moisture (water) condition in the pavements of roads in Europe, from the Alps and northwards, as a consequence of climate change;
- estimate the likely consequences for pavement and subgrade material behaviour and for whole pavement needs in terms of: (1) reformulation of material composition, (2) new and modified drainage practice, (3)modification to maintenance practice and rehabilitation;
- perform this study for a range of representative pavement types (asphaltic, unsealed, intercity, county, low-volume) and representative climatic zones (temperate maritime, temperate Mediterranean, continental warm summer, continental sub-arctic);
- assess uncertainties to permit risk / vulnerability to be evaluated;
- define options for responding to the changes, identifying key selection criteria;
- perform exemplar cost-benefit analyses to allow road owners to detrermine best options for their own situations;
- formulate findings into a wide range of formats (published, brochure, web, educational, email) and disseminate them accordingly.
The project will be performed by a combination of literature review, laboratory evaluation of materials, computational studies of pavement structural and hydrological performance and by the development of recommendations suitable for implementation by national road owners into their specifications and design guides. An advisory panel drawn form a selection of national road authorities will be assembled to advise on goals and progress and to critically examine the outputs to permit their improvement.
It is noted that the life cycle of the pavement is much less than the time span over which climate change will have a statistically dependable influence on pavement performance. Only for the pavements with longest life, or for the lower layers that may not be touched during future rehabilitation and reconstruction, does the current designer need to change his or her practice at present. However, if current practice were not to be progressively changed at times of major pavement rehabilitation during the next 110 years, then the effects of these changes on pavements constructed, managed and trafficked as at present might be as follows.
- In areas where rainfall is unchanged then subgrades and aggregate layers should be dryer than as at present, on average, because warmer temperatures should generate greater evaporation. Even in wetter areas, the increased rainfall intensity is likely to result, for a road in moderate or better condition, in greater run-off. Then increased net infiltration to the subgrade and aggregate should be small or even negative. A neutral effect or even a small improvement in pavement support is therefore anticipated in most locations.
- Temperature and rainfall increase will be a challenge for asphalts. Softer materials more prone to rutting and stripping can be expected.
- In those countries that rely a lot on having frozen roads during winter, the length of the frozen period will reduce in the far north with a reduced length of spring thaw – a mixed problem and benefit. To the south, in much of the Nordic countries, frozen winter road structures may disappear altogether, in some years. In other years, periods during the winter season when the pavement surfaces are thawed will P2R2C2 – Overall Advice & Summary Report – October 2010 Page 4 of 21 become the norm. For this reason, many thin and unsealed pavements will need upgrading to provide reliable high bearing capacity all winter long. Those thaw problems concentrated in the spring will be likely to become less problematic,
- In coastal and low lying areas raised water tables may be experienced due to points at which flood waters collect or due to raised sea levels. Road raising or special reinforcement techniques will be needed locally to address this problem.
The appropriate responses to these changes in pavement performance:
- will be achievable, in most cases, by routine material formulations that can be employed at the next reconstruction/rehabilitation event,
- will need new design criteria regarding temperature and return period of storm flows to be developed (regionally specific),
- will need more attention paid to drainage systems, particularly to make them selfcleaning and easily inspectible,
- may necessitate more rut-resistant and stripping-resistant resurfacings on ‘perpetual pavements’ than originally planned. Such materials are readily available at a minimal cost differential, and
- are likely to include, in the mid and southern parts of the Nordic countries, stabilisation of unsealed pavements, or overlaying by bound layers.
However, concentrating on these technical issues is unlikely to be a significant problem, nor a great economic challenge when compared to the necessary response from highway engineers to the wider social, economic, technical and political impacts on pavements that can be guessed at over the next 110 years. Demographic change, transportation method, funding models, journey patterns, vehicle type, demands of users and demands of funders are expected to be far more of an influence on future pavement engineering. Some of these influences will likely be driven by climate change itself.