Van Houten and Nau demonstrated that a warning program which included the use of special information flyers and warning tickets enhanced the effectiveness of signs providing feedback on the percentage of motorists not speeding. Study subjects were motorists traveling on 14 Haifa streets between 09:00 and 16:00 hours on Sunday through Friday. All streets were selected because of a high level of speeding behavior and serious accidents. Introduction of the enforcement package produced a reduction in the percentage of motorists traveling 10 km/h and 20 km/h over the speed limit on all 14 streets. The mean reduction in the percentage of motorists traveling 10 km/h or more over the speed limit was 48.1 percent, with a range of 16 to 73 percent. The mean reduction in the percentage of motorists traveling 20 km/h or more over the speed limit was 64.3 percent, with a range of 50 to 80 percent. During the 6-month period following the introduction of the enforcement program, there were 13 accidents and 16 injuries on the side of the 14 streets where the program was applied. During the preceding 2 years, there were 33 and 37 accidents during the same 6-month period in this direction and 53 and 45 injuries. The experiment results suggest that the program produced sufficiently long lasting effects to warrant its use. Tabular data and seven references are provided.