The object of this study, over two winters from 1992 to 1994, was to investigate how drivers' behaviour is changed when they start using studless winter tyres instead of studded tyres. 120 drivers were selected at random from vehicle register. One matched group were given studded tyres and the other studless winter tyres. Dependent variables were effects on exposure, driving speeds, use of brakes and keeping headways. Driving behaviour was monitored through two instrumented cars. Subjects drove route of about 80 km twice in first winter and once the second winter. Computers recorded speeds, use of brakes and headways. The purpose of study was not revealed to drivers until after the last task. Exposure such as number of trips was not affected. Driving speeds of studless drivers increased, especially in good driving conditions on motorways. On sharp curves studless drivers slowed down more than studded drivers. On slippery secondary roads studless drivers used brakes more softly. Headways of both groups were monitored in second winter. Studless drivers were keeping on average 11 m longer headways. Results of study suggest that changing to studless tyres does not markedly change speeds in the long run. Studless drivers do however drive more carefully in conditions which they experience as difficult or demanding more attention.
Samenvatting