Rolling resistance evaluation of winter tyres on in-service road surfaces

Rolling resistance, the energy dissipated due to the rolling movement of a pneumatic tyre over a surface, is a relevant factor that should be considered when aiming at a more energy efficient road infrastructure as well as for reducing CO2 emissions. The energy dissipation, as a result mainly of hysteretic losses, is dependent on the tyre, on the road surface, and operating temperature, among other factors. In this paper, 50 different tyres of five different types (all season tyres, summer tyres, winter tyres without studs, winter tyres with studs and winter tyres with hard particles) were evaluated with respect to rolling resistance on two different road surfaces, at three different test speeds and different states of tyre wear. In addition to the full-scale field tests, a drum facility was used to evaluate rolling resistance of the same tyres in a more controlled environment. This resulted in more than 500 measurements that were analysed in this paper. Earlier, no data regarding rolling resistance of studded winter tyres have been published and there have been very few studies, if any, comparing measurements on drums with measurements on road pavements. In the field, rolling resistance was significantly depending on tyre type, and many tested tyres performed differently on the two surfaces. No significant correlation was found between labelled tyre values and rolling resistance measured on roads, nor between rolling resistance measured on roads and on a drum facility. Better correlations were found between labelled tyre values and our own drum results. This calls for a review of the relevance of the energy labelling procedure.QC 20200505