Naturalistic Experimental Analysis of Driver Compliance With Posted Speed Limits

The current study assesses the effects of three interventions commonly used by law enforcement officials to increase driver compliance with posted speed limits and thereby reduce speeding. In two multiple-treatment single-case research designs, motorist speeds on two rural roads in a midwestern state were observed and measured during baseline (no intervention) and during exposure to three interventions: a stationary speed trailer, an unmanned police vehicle, and traditional police enforcement. Interventions were counterbalanced across locations and data aggregated according to intervention type. Results suggests that although two of the three commonly adopted methods had no consistent impact on driver speeds, the unmanned police vehicle intervention yielded increases in compliance compared to baseline for both sites. Implications for small-scale traffic research are discussed.