Geographical distribution of road slipperiness in Sweden, on national, regional and county scales

Abstract

ABSTRACT:The influence of latitude on the distribution of slipperiness of roads in Sweden was studied at three scales: national, regional and county. Data from 654 Road Weather Information System (RWIS) stations were compiled over five winter seasons, from 1998/1999 to 2002/2003. The aim of the study was to establish a basis on which to model how future climate changes might affect frequency of slipperiness and costs for maintenance in winter. Four types of slipperiness were studied (slippery conditions due to moderate (HR1) or severe (HR2) hoarfrost, moist/wet surface that freezes (HT), and rain or sleet falling on a cold road (HN)), all adding up to form the winter index (WI).In Sweden, the distribution of slipperiness varies depending on the scale (national, regional or county). On the national and regional scales the mean temperatures give a general picture of the total slipperiness -i.e. dependence on latitude; different factors were tested and latitude proved to be the most correlated. Slipperiness caused by HR1 and HR2 hoarfrost tends to increase towards the north, while road icing (HT) decreases. On the county scale, neither latitude nor any other tested geographical variable, could explain much of the variance. Local climate and the directions of movement of individual weather systems may be more important. The regional scale is considered to be most suitable for future modelling of the influence of the effect of a changed climate on the slipperiness of the roads.

The use of a temporal analogue to predict future traffic accidents and winter road conditions in Sweden

“…Different types of slipperiness For this study, road slipperiness has been subdivided into four types in which the road surface temperature should be lower than 0°C. These four categories are the same as used by Andersson et al (2007), with a minor change to the +1°C threshold to 0°C and are based on the scheme used by the SRA in their decision-making for maintenance activities, i.e. salting or ploughing (Möller, 2002).…”

“…salting or ploughing (Möller, 2002). The different slipperiness types have the following definitions (for further details see Andersson et al 2007):…”

On the relationship between the risk of hoar frost on roads and a changing climate in Sweden

“…The clustering algorithm failed to associate around 30% of the occurrences of hoar frost with a known cause. This may be due to large variations in temperature over short periods of time (e.g., Gustavsson, 1991), especially in the north of Sweden (e.g., Andersson et al, 2007). This may lead to the occurrence of hoar frost with a preceding period shorter than 5 hr (e.g., a short reaction time), which cannot be classified by the current scheme used in this study.…”

“…Of these types, hoar frost is generally associated with high accident rates (e.g., Wallman and Åström, 2001). The influence of hoar frost on traffic safety has been reported in many countries in the Northern Hemisphere, such as United States (Takle, 1990;Greenfield and Takle, 2006;Toms et al, 2017), Canada (Crevier and Delage, 2001), United Kingdom (Hewson and Gait, 1992;Andersson and Chapman, 2011b), Russia (Bulygina et al, 2015), Poland (Gałek et al, 2015) and Sweden (Gustavsson and Bogren, 1990;Karlsson, 2001;Andersson et al, 2007). Of these countries, Sweden suffers severe hoar frost problems (Gustavsson and Bogren, 1990;Hewson and Gait, 1992).…”

Winter hoar frost conditions on Swedish roads in a warming climate

“…Hoar frost, which forms on the road surface as a result of direct desublimation, reduces surface friction (Karlsson, ) and can lead to traffic accidents. The influence of hoar frost on traffic safety has been reported in many countries in the northern hemisphere (e.g., Gustavsson and Bogren, ; Takle, ; Hewson and Gait, ; Karlsson, ; Greenfield and Takle, ; Andersson et al, ; Bulygina et al, ; Galek et al, ; Toms et al, ). Of these countries, Sweden suffers severe hoar frost problems (Gustavsson and Bogren, ; Hewson and Gait, ).…”