The main objective of IRWIN is to develop an improved winter road index capable of assessing the implications of climate change in various weather parameters and also related road maintenance actions.
Climate change scenarios have so far been calculated based on ordinary meteorological data, which have large limitations with respect to resolution. The idea of IRWIN is to combine the best traditionally made climate scenarios with the much more accurate spatial data from field stations in the Road Weather Information systems (RWIS) installed in most northern hemisphere countries.
Once a good quality observational database was completed, the climate downscaling task was started to establish the climate database. Weather classes were developed to select the historical analogue days matching the future days.
The final phase of the project developed a winter index technique to evaluate temporal and spatial variations of some weather parameters and corresponding winter maintenance needs. The results showed that temperature would increase most in the northern areas in Sweden and Finland. Same areas will experience a larger amount of events when there is a shift from plus to minus degrees, and therefore need more maintenance due to slipperiness caused by this shift. Only the region in southwestern Sweden will in the future have fewer days when temperature shifts from plus to minus degrees due to a warmer climate in that area.
The future will bring more rainy days on a cold surface in the north due to the milder climate and more rainy days in the north instead of precipitation falling as snow. The northern areas will also experience more slipperiness due to frost days when the surface temperature is low and the dew point is larger than the surface temperature. These frost days will occur less frequently in the future in the more southerly areas, due to fewer days with minus degrees. Higher temperatures will also result in precipitation falling as rain instead of snow, which can be seen as a large decrease of ploughing events indices.
The need for maintenance operations will change in the different regions as the climate changes. A warmer climate can both mean more needs for salting due to more slippery roads but at the same time less ploughing events when precipitation falls as rain instead of snow.
The index developed in this study has shown to be a useful tool for future maintenance operations. It can give valuable information to stakeholders as to where and when measures need to be taken. Possibilities were also investigated of using road weather data from other ERA-NET countries to perform similar calculations. Similar assessments could be done relatively easily if enough road weather information was archived and available. Taken into account the seriousness of climate change and its implications, it is highly recommended that Road Owners if not yet do so, start operational archival and quality control of all road weather observations in their countries. Standardisation of data formats is also recommended.
