Road Safety Analysis in the United States

Abstract

The Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users required each of the states to develop a strategic highway safety plan and establish a Highway Safety Improvement Program (HSIP) as a core program. The HSIP required states to submit annual 5% reports describing at least 5% of their most hazardous locations, approaches being used to improve safety at these locations, and their effectiveness in improving safety. A review of FHWA's 2009 5% reports indicated that most state departments of transportation were still using basic safety analysis procedures such as frequency, rate, or safety index. Understanding that traditional methods are fraught with issues, biases, and false assumptions, recent research has opened doors to more advanced methodologies in the form of two safety analysis tools: SafetyAnalyst and the Highway Safety Manual (HSM). Unlike basic traditional methods, the empirical Bayes approach used in these tools involves rigorous calculations and requires safety performance functions in addition to roadway characteristics, traffic volume, and crash information. The data requirements and statistical complexity of these new safety tools are considered by many a hindrance to their adoption, but the levels of increasing complexity with additional requirements allow states to adopt at their own speed. The intent of this paper is to document the current engineering-related safety analysis practices and states’ perspectives toward adopting and implementing SafetyAnalyst and the HSM. The perspectives of several states on implementation of SafetyAnalyst were obtained through a survey and are discussed in this paper. This survey mainly helps the practitioners, administrators, and researchers to understand the various engineering-related safety analysis methods used across states and the states’ perceptions on shifting to newer tools.