Drivers travelling during the week between 10:30 and 10:50 a.m. and 2:30 and 2:50 p.m. on a four-lane undivided highway entering a residential area of Dartmouth, Nova Scotia were involved in an experiment to see if a prompt would be sufficient in reducing their speeding behavior. The prompt consisted of a large sign that was positioned 2 meters from the side of the road and 2.3 meters above the ground. The sign looked similar to other Nova Scotia Department of Highway signs. During each step of the study, which used a reversal design, a radar antenna concealed in a yellow litter can placed approximately 0.5 km inside the 50 km speed zone monitored the speed of passers-by. In addition, to increase the degree of experimental control, the frequency of police patrolling the area remained constant. The first step of the research, baseline 1, consisted of recording daily vehicle speeds at the specified times described above. Next, daily posting 1 was carried out. This step required the installation of the prompt. It was set up next to the 50-km speed limit sign. The prompt indicated the percentage of drivers travelling at 66 km/hr or less during the previous day and the highest percentage of non-speeding drivers recorded to date. During baseline 2, the sign was covered while speeding sampling continued to be collected. Daily posting 2 followed-a repeat of daily posting 1. Then a new condition was tested, the no-number phase 1. The prompt remained visible, but numbers were absent. Thereafter, the daily posting 3 was executed. This included the same procedure as the preceding daily postings. A no-number condition was subsequently assessed. Then instead of a daily posting condition, a weekly posting took place. The message on the prompt changed to "Drivers Not Speeding Last Week" and the percentage values were only changed once a week. The radar sampling, however, continued on a daily basis. A third no-number condition was carried out followed by a second weekly posting. Lastly, a 26 week follow-up phase was administered. This condition measured the speed of the drivers at 10:30 and 2:30 for 20 minutes just like the previous sampling; however, the sampling was executed only on a randomly selected day each week. The prompt showed the same message as the preceding weekly posting sessions, but displayed the weekly random figures.
Analysis of the radar sampling accumulated throughout the experiment revealed that the presence of the prompt when presenting numerical feedback was effective at reducing the speeding behavior. Both weekly and daily posting conditions contributed to this, decrease. On the other hand, when the “no number” conditions were used, the motorists returned to baseline levels (e.g., they increased their speeding behavior). The authors suggest that more research is required to evaluate whether public posting of the number of vehicles speeding can deliver a sustained reduction in speeding.