Samenvatting
A counterbalanced, reversal design was used to compare the effectivess of posted feedback and increased police surveillance in reducing speeding on two urban highways. Drivers' speeds were measured using a con-cealed radar unit. During public posting, a large highway sign, which listed the percentage of drivers not speeding during the preceding week and the best record to date, was erected on each street. Use of the feedback sign alternated with periods of baseline and periods of increased police sur-veillance and ticketing.