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C H A P T E R 2 Study Design The study design elements have been defined from a variety Traffic-, roadway-, and environment-based questions. of perspectives to try to make certain that there is sufficient Roadway data will be collected in the Roadway Data Col- statistical power to detect statistically significant effects in as lection effort (S04). Front-mounted radar combined with many cases as possible. In this way, the data produced by the the images from several synched video cameras will pro- study will be able to answer as many of a comprehensive set vide traffic information. Environment-based questions can of categorized research questions as feasible, while staying be addressed in several ways. Information will be available within the bounds of known project constraints such as fund- about time of day, ambient illuminance levels, windshield ing and time. These constraints serve to limit the project in wiper status, and, for select crashes, the relevant details several ways, such as the duration of the data collection and of the crash site will be documented by a trained crash the number of data collection sites that can be established site investigator. and managed. Vehicle-based questions. Vehicle details, including make, The set of research questions has guided decision-making model, and year, as well as all onboard safety features, will processes throughout the design of the SHRP 2 NDS. Addi- be documented for each vehicle in the study. tionally, sampling statisticians and other experts were con- Driver- or driver-error-based questions. Each primary sulted in the development of the sample design and contractor driver in the study will be characterized in terms of his or site-selection process. Each of these elements, together with her demographic details. In addition, each primary driver the process for participant recruitment, is discussed below. will undergo a fairly extensive suite of assessments designed to characterize him or her along various driving-relevant dimensions of ability (e.g., visual perception). In addition, Specific Research Questions continuous video will be collected from four cameras. These On the basis of numerous source documents, including The can be reviewed for any event of interest to address error- 100-Car Naturalistic Driving Study, Phase II (Dingus et al. based questions. 2006), the Tri-Level Study of the Causes of Traffic Accidents Passenger-based questions. A fifth camera will be aimed Final Report (Treat et al. 1979), and Pre-Crash Scenario Typol- to capture an irrevocably blurred still image of the cabin ogy for Crash Avoidance Research (Najm et al. 2007), as well every 10 minutes. This is done to capture basic information as expertise from researchers in the transportation safety on the number of passengers as well as an approximation field, 392 research questions were identified for considera- of their ages and genders for each trip. tion in the NDS design. These questions address different Infotainment-system-based and nomadic-device-based types of crashes and other noncrash-specific safety areas questions. Information on Infotainment system status will of interest. They also provided the basis for making a variety be available from the controller area network (CAN) bus for of decisions regarding the number and types of DASs used to some of the vehicle fleet. Nomadic device (e.g., handheld collect data during the study, the types and priority of addi- technology, such as a cell phone) usage can be determined tional sensors and DAS capabilities, and the sampling and using appropriate sampling schemes, though hands-free analysis trade-offs. usage will be more difficult to reliably detect. The questions were subcategorized into the following per- Aggressive-driving-based questions. Aggressive driving spectives (the list also includes examples of study design deci- patterns can be seen in the exceedance of preset (but sions intended to address the questions, as applicable): adjustable) levels of various sensors or combinations thereof 7