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7C h a p t e r 3 The main goal of Phase I of this project was to identify and prioritize research questions in order to focus resources for Project S08. Detailed information is available in Appendix A, but for the sake of context the methodology is summarized below. The project team considered using research questions developed by S01 and S05 researchers, as well as other meth- ods to identify additional research questions. Other meth- ods included holding focus groups with traffic safety experts, developing research questions related to each major crash type, and reviewing existing driving safety literature. However, feed- back from SHRP 2 indicated that the S01 and S05 researchers had already devoted significant resources to developing appro- priate research questions. As a result, the 56 research questions from the S01 reports and the 392 questions from the S05 report were used as the source for research questions. These research questions were organized into groups according to common- alities in categories of explanatory (or independent) variables corresponding to environmental, driver, vehicle, roadway, and nondriving factors. The variables were further categorized according to their static or dynamic characteristics and safety outcomes. The groupings reflect a systems-based perspective that considered driving safety implications and the feasibility of potential safety interventions. A decision tree was created to provide a systematic mecha- nism for prioritizing the global research questions. The deci- sion tree emphasized questions that provide greater insights about drivers, that appear to support safety interventions, and that provide insight into large-scale morbidity and mor- tality consequences. Each global research question was evalu- ated using the decision tree to determine a priority ranking. More details about the decision tree and the prioritization of global research questions can be found in Appendix A. Of the 27 global research questions, 16 addressed the goals of SHRP 2. The other 11 were beyond the scope of SHRP 2âs focus on safety research or were condensed into more rep- resentative global questions. In Phase II the global research questions have been revised through several iterations with selected reviewers. They are presented here in a form slightly modified from that of the Phase I report. The central themes of the questions relate to the influence of driver behavior on crash likelihood, the influence of roadway improvements on crash likelihood, and how to define good crash surrogates. Eight of the SHRP 2ârelevant questions have been identified as having the highest priority. (The Phase I report had nine high-priority global research questions. The team removed one question related to dynamic driver characteristics [as opposed to static characteristics such as age or gender] because the team later determined that distraction, fatigue, and impairment [which are captured in the other research questions] are already exemplars of dynamic driver charac- teristics.) The unranked list of eight questions is as follows: ⢠How do driver interactions with roadway features influ- ence the likelihood of lane-departure crashes? ⢠How do driver interactions with intersection features (configuration and operations) influence crash likelihood? ⢠What is the influence of driver impairment (e.g., alcohol) on crash likelihood? ⢠How does driver distraction influence crash likelihood? ⢠How does driver fatigue influence crash likelihood? ⢠How do driving behaviors influence crash likelihood? ⢠How do advanced driver support systems influence crash likelihood? ⢠What variables or pre-event factors are the most effec- tive crash surrogate measures? What explanatory factors are associated with crashes or crash surrogates? And what analytical models can be developed to predict crashes or crash surrogates? The last global research question is particularly important and related to the other seven. The development of surrogate measures can provide insights on crashes when there are too few actual crashes to complete an effective analysis. Because demonstrating effective crash surrogates can support other means for addressing important research questions on driver safety, this is considered one of the highest-priority questions. Overview of Phase I: Analysis Plan
