Why did the accident involvement of young (male) drivers drop about 50%?

In the Netherlands during 1990-92, a sharp reduction occurred in the number of kilometres driven by young male drivers, both students and non-students. The paper examines the reasons for this and the resulting considerable decrease in serious accidents of some 45% for men compared with 36% for women. Car ownership is said to have had an influence on kilometres driven although the introduction of FPTP (Free Public Transport Pass) for students has probably also had influence on accident rates by reducing accident exposure