Effects of a penalty point system on traffic violations

We analysed data from the Norwegian driver's licence penalty point register over a three-year period, in order to investigate whether the number of incurred penalty points in a given time period can predict the probability of incurring additional points in the subsequent period. Data for all category B drivers without penalty points at the start of the study period were included in the analyses. Norway's penalty point system implies that speeding and various other traffic violations result in two or three penalty points for full-license drivers and four or six points for probationary-license drivers. Eight points within a three-year period results in a six-month disqualification. Two hypotheses were formulated: 1) A "driving style effect" implying that drivers with previous penalty points have a higher probability of incurring new points than drivers without previous points; and 2) a "deterrence effect" implying that drivers with more than four points have a reduced probability of incurring new points, due to impending risk of license revocation. Results showed an inverted U-shaped relationship between number of penalty points incurred during a one-year period and the number of additional penalty points incurred in the subsequent year, with the highest number for drivers with four previous points. Thus, both hypotheses were clearly supported, and it is concluded that the penalty point system has a significant deterring effect for drivers who are at high risk of losing their license at the next infraction.