Abstract
Complications in formulating an analytical model of the dependence of accident phenomena on traffic conditions which includes every essential factor means that a comparison between traffic risk when no limit is applied and when a speed limit is in force cannot be made solely by applying a unequivocal theory to the available data. This is due to the fact that many essential causality problems relating to traffic accidents have not been investigated, and that there is to believe that a great deal of the psychological phenomenology cannot be parameterise and described by mathematical methods. Due to these reasons this report cannot claim to be more than of a descriptive character.