FEHRLopedia

Anticipated climate change in Europe, north of the Alps, over a 110 year period from the mean climate in 1960-1990 to the mean climate in 2070-2100 was estimated using two emissions scenarios and two computational approaches. The likely impact of the resulting changes in climate was then estimated for a range of pavements and pavement-related infrastructure in order to determine the consequences for road owners.

The predictions of climate change showed that there is considerable local variation, as described in one of the supporting reports. Nevertheless, it is possible to summarise the predicted principal manifestations of climate change in the study region as:

• Temperature rise. In the southern edge of the study area the greatest deleterious impact of this will be hotter summers. In the far north the greatest impact will be on the reduction of the length of the winter. In most of the Nordic countries and northern Poland the principal deleterious effect will be the reduced number of zero degree transitions meaning pavements will spend significant lengths of time nonfrozen at the surface during the winter season.

• Little change in total rainfall (or snowfall) except in northern Poland, the Baltic and Nordic states and Scotland. Greatest increases are expected in the Atlantic coastal areas of Norway and Scotland but, proportionately to current rainfall levels, the increase there will be similar as in other parts of northern Europe – 20-30%. The Alps will also experience an increased precipitation.

• Increased rainfall intensity in most areas.

At the time of writing the political will to ameliorate change seems relatively small, so the estimated climate changes computed, and on which this report is based, may be an underestimate of those that will be experienced.

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 willbecome 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,

a) will be achievable, in most cases, by routine material formulations that can be employed at the next reconstruction/rehabilitation event,

b) will need new design criteria regarding temperature and return period of storm flows to be developed (regionally specific),

c) will need more attention paid to drainage systems, particularly to make them selfcleaning and easily inspectible,

d) 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

e) 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.