Parents are the key to improving teen driving safety.
It is a well-known fact that experience is important for safe driving. Previously, this presented a problem since experience was mostly gained during the most dangerous period of driving-the first years with a licence. In many countries, this "experience paradox" has been addressed by providing increased opportunities to gain experience through supervised practice. One question, however, which still needs to be answered is what has been lost and what has been gained through supervised practice. Does this method lead to fewer accidents after licensing and/or has the number of accidents in driving practice increased? There were three aims in the study. The first was to calculate the size of the accident problem in terms of the number of accidents, health risk and accident risk during practising. The second aim was to evaluate the solution of the "experience paradox" that supervised practice suggests by calculating the costs in terms of accidents during driving practice and the benefits in terms of reduced accident involvement after obtaining a licence. The third aim was to analyse conflict types that occur during driving practice. National register data on licence holders and police-reported injury accidents and self-reported exposure were used. The results show that during the period 1994-2000, 444 driving practice injury accidents were registered, compared to 13657 accidents during the first 2 years with a licence. The health risk during the period after licensing was 33 times higher and the accident risk 10 times higher than the corresponding risk during practice. The cost-benefit analysis showed that the benefits in terms of accident reduction after licensing were 30 times higher than the costs in terms of driving practice accidents. It is recommended that measures to reduce such accidents should focus on better education of the lay instructor, but not on introducing measures to reduce the amount of lay-instructed practice.