The effect of manipulating movement-illusion-inducing stimuli on reducing traffic speed on horizontal curves

This study assessed the effectiveness of pavement markings painted along the curbs of a two-lane street on reducing driving speed around a curve. Three different types of marking patterns were investigated in a single-case design. The velocity and perceived speed of vehicles passing through a frequently used entrance road on a university campus were measured. Velocity was measured by recording the time it took vehicles to travel 150 ft (45.7 m). To measure perceived speed, volunteer observers rated the speed of videotaped vehicles using a 15 item questionnaire developed for this study. Data were collected only on passenger vehicles during clear weather conditions. The velocity measure indicated that markings, particularly those in a checkerboard pattern, were effective in reducing the number of drivers exceeding 35 mph. This outcome is consistent with the findings from previous studies with similar interventions. The perceived speed measure did not show meaningful trends across phases. Future research with this type of inexpensive intervention and the need to develop a valid and reliable measure of perceived speed, which takes into consideration safety factors in assessing driving behavior, is discussed