For many years, the approach to reducing motor vehicle injury and death has been the "3-E" approach of engineering, education, and enforcement. Crash incidents have determined which roadways need improvements, where and what to enforce, and what public information and education should be conducted. At the Montana Department of Transportation, reports of crashes with resulting injuries, fatalities, and/or property damage are analyzed much as departments of transportation throughout North America. Also included in the analysis is consideration of Average Daily Traffic (ADT) volume. Results of the analysis are used to determine sections of roadways with high crash incidents where engineering "fixes" may reduce the number of crashes. This same crash and ADT data can also be used to determine what enforcement and educational actions could impact on the crash problem. This article discusses how, as predicted in risk homeostasis theory, solving some 3-E problems can cause unanticipated consequences that can impact on overall crash rate reduction efforts.
Abstract