Abstract
Since January 1, 1987 the use of retroreflecting circles on the wheels of bicycles is mandatory in the Netherlands. Before the introduction of the legislation about 25% of the bicycles had side reflection. After the introduction of the legislation, side reflection increased to about 73% at the end of 1988 and this number is still slowly increasing. After the introduction there is a significant (relative) decrease of about 5% of the number of cyclist traffic victims in darkness or in twilight.