Abstract
The seat belt usage of drivers was observed at the entrance to two campus parking lots during morning arrival times. After 11 days of baseline, fliers which prompted seat belt wearing were handed to drivers of incoming vehicles. At one parking lot all fliers offered a chance to win a prize (noncontingent rewards); while at the second lot only those fliers given to seat belt wearers included a chance to win a prize (contingent rewards). The analysis of repeated exposures per individual verified that only contingent rewards influenced substantial increases in belt wearing and showed that most of the influence occurred after the initial incentive prompt.