Assessing the Safety Impact of Roadway Improvements Using Naturalistic Driving Data--Feasibility Study

This project explored the feasibility of using Second Strategic Highway Research Program (SHRP 2) data, including the Roadway Information Database (RID), to evaluate the effectiveness of roadway safety improvements where traditional crash data are limited. The research team conducted two case studies based on naturalistic driving study (NDS) data from 200 trips. The two case studies evaluated the safety effects of (1) a paving project with newly installed pavement and markings, and (2) a median barrier replacement project with a newly installed and restored concrete median. A number of safety surrogate measures were used to develop a comprehensive understanding of how driver behavior changed with and without the safety treatment. The results from both case studies indicated that the roadway improvements had an impact on driver safety behavior, as indicated through the surrogate safety measures of speed, lateral and longitudinal accelerations, lane deviation, and car-following behavior. The two case studies illustrate two different methods for studying the effectiveness of roadway improvements on safety. The paving project case study compared driver behavior data collected at the project site after the roadway improvement with data from an adjacent site with similar roadway conditions but without the pavement improvement. The median barrier project case study compared data on the same segment of road before and after the improvement project. The two different methods illustrate the flexibility available with SHRP 2 safety data. In addition to the case studies, the research team also assessed the availability, suitability, and limitations of SHRP 2 and RID data for evaluating the safety impact of roadway improvements.