OBJECTIVE: The aim of the study was to compare the safety effects of studded and unstudded winter tyres based on fatal road accidents.
METHODS: The data included 958 road accidents involving a passenger car or van that occurred in Finland from November to March between 1997 and 2012.
RESULTS: Comparing the proportions of winter tyre type in accidents and in general traffic showed that the overall effect of tyre type on the number of accidents was not significant, although studded tyres reduced fatal accidents by 10-15%. Compared to unstudded tyres, studded tyres reduced accidents significantly only on bald ice in 2005-2012. Drivers using unstudded tyres were more experienced and their profession was more frequently related to driving. Also, the vehicle age was lower for vehicles with unstudded tyres. On the other hand, the state of repair was less pertinent for unstudded than for studded tyres. These confounding factors offset their effects to some degree.
CONCLUSIONS: The risk of fatal road accidents in winter between studded and unstudded tyres does not differ significantly. However, the accident risk has recently been substantially higher on bald ice for unstudded than for studded tyres. The magnitude of this risk difference is difficult to determine without specific information on exposure by road surface.