The objective of this work has been to go beyond standard road grip studies, and instead investigate how the driver's possibility to deal with one challenging situation depends on the tyres and tyre configuration. This study utilised a novel methodology where measurements of different tyres on ice in VTI´s tyre test facility enabled a simulator study for evaluating the impact of different tyre characteristics when driving in conditions with strong side wind on a slippery road.
A driving simulator scenario was chosen where the driver is exposed to strong side wind gusts, when driving at high speed on an ice covered road. To collect data from different tyres VTI's tyre test facility was used. The measurements were used to create a model that characterises the wheel, and which could be used for a real time simulation. For this Pacejka's magic formula in combination with a model to account for the tyre relaxation length was used. A bus vehicle model was implemented in Sim II, and the experiment was conducted with five test persons. Each person had to drive on a straight ice covered road, experiencing sudden wind gusts of different strength, while using different tyre combinations.
To deal with strong side wind, good front wheel grip is most important, and while non studded winter tyres provided little or no improvement over summer tyres, studded winter tyres significantly reduced the risk to run off the road. Furthermore, it is very difficult for the drivers to judge, beforehand, whether a vehicle with a particular tyre configuration will perform good or bad.
Hjort, M. & Jansson, J. (2008). Handling of buses on slippery roads during the influence of side wind – a study of the effects of different tyres. AAP – in press
Hjort, M., Thorslund, B., Sundström, J., Wiklund, M. & Öberg, G. (2008) Traffic safety of buses wintertime. VTI rapport 618, Linköping, Sweden, VTI. (In Swedish)