Drivers who were free of collisions and convictions over the year preceding license expiration were sent a letter notifying them of a one-year license extension issued as a "reward" for this accomplishment. They were also told that at the end of the following year, should their records again be clean, they would be recontacted and given a second extension. The results of this reward program indicated no reliable effect on subsequent traffic convictions, and various detrimental effects on subsequent collisions, for drivers in the program as compared to uncontacted controls. The detrimental effects were not significant for drivers whose prior records were clean for three entire years, suggesting that a one-year period was not a sufficient barometer of a person's driving. Drivers having one or more prior entries were involved in an incentive program. These drivers were sent a letter describing their eligibility for a one-year license extension, which would be granted provided that their records remained free of collisions and convictions over the subsequent year. The results of this incentive program indicated no significant effects on subsequent convictions but various beneficial effects on subsequent collisions for drivers in the program, as compared to controls.