NHTSA’s mission is to prevent motor vehicle crashes and reduce injuries, fatalities, and economic losses associated with these crashes. To carry out this mission, NHTSA conducts a range of safety-related activities, including setting vehicle safety standards; investigating possible safety defects and taking steps to help ensure that products meet safety standards and are not defective (through recalls if necessary); providing guidance and other assistance to states to help address traffic safety issues, such as drunk driving and distracted driving; and collecting and analyzing data on crashes. In fiscal year 2014, NHTSA’s enacted budget was $819 million. NHTSA collects and analyzes crash data for a variety of purposes, such as to determine the extent of a safety problem and what steps NHTSA should take to develop countermeasures. NHTSA collects data through detailed, in-depth investigations as well as to generate national statistics and nationally representative data, as shown in table 1. As mentioned previously, this report focuses on NASS-CDS. NHTSA collects NASS-CDS data through in-depth investigations of a sample of police-reported motor vehicle crashes that occur in the United States. The data collected through NASS-CDS are detailed and descriptive and allow NHTSA and others to assess the crashworthiness of different types of vehicles, evaluate different vehicle safety systems and designs, and understand the nature of injuries that people sustain during crashes. NHTSA uses the data collected as part of NASS-CDS for statistical analyses in its rulemaking and to estimate the size of the population that might be affected by its rulemaking. NHTSA also uses NASS-CDS data for other purposes, such as to identify existing and potential traffic-safety problems. For example, NHTSA has used NASS-CDS data to investigate patterns of roof intrusion into a vehicle resulting from real-world rollover crashes. According to NHTSA, NASS-CDS data showed that the damage and intrusion that occurred during real-world crashes was greater than the damage and intrusion that occurred during crash tests, pointing to the need to revisit NHTSA’s standards for the strength requirements for a vehicle’s roof. Others, including other federal agencies, universities, research institutions, and the automobile and insurance industries, use NASS-CDS data to understand the nature and consequences of real world crashes. For example, the National Transportation Safety Board, an independent federal agency, uses NASS-CDS data for research purposes as well as for conducting its accident investigations, whereas automobile manufacturers may use NASS-CDS data to study crash patterns and how those patterns have changed over time in order to prioritize their own research on vehicle designs and safety features. NHTSA collects NASS-CDS data and information using stratified sampling—a statistical method of sampling in which a population is divided into two or more parts (called strata) and a sample is selected from each part (or stratum). NASS-CDS, specifically, is a stratified, three- stage probability sample, as illustrated in figure 1. The first stage of the NASS-CDS sample was the selection of PSUs—the geographic locations where NHTSA collects data. NHTSA defined the PSUs so that their minimum population was approximately 50,000, and each PSU consisted of a central city, a county, a group of counties, or a portion of a large county excluding a central city. The PSUs were grouped into 12 strata based on geographic region (i.e., Northeast, South, Midwest, and West) and urbanization type (i.e., large central cities, large suburban areas, all others). The PSUs to be sampled were allocated to each stratum roughly proportional to the number of crashes in each stratum, and at least two PSUs were then selected from each stratum. As of 2014, a total of 24 PSUs comprised the NASS-CDS sample, as shown in figure 2. The second stage was the selection of police jurisdictions within the sampled PSUs. About 170 police jurisdictions across the United States are part of the NASS-CDS sample and the number of jurisdictions per PSU varies (e.g., the Seattle, Washington PSU has two police jurisdictions in its sample, whereas the King County, Washington PSU has seven). Each police jurisdiction was assigned a “measure of size” that reflects the number, severity, and type of crashes in each jurisdiction. A sample of police jurisdictions was then selected from each sampled PSU, and those jurisdictions having a larger measure of size were oversampled. The third and final stage is the ongoing selection of the actual police accident reports that are filled out by a police officer at the scene of a motor vehicle crash. Each week, the sampled police jurisdictions are contacted and all police accident reports that have accumulated since the previous week are reviewed and classified into a stratum based on the types of vehicles involved, most severe police-reported injury, disposition of the injured, tow status, and model year of the vehicles. To be eligible for inclusion in NASS-CDS, a motor vehicle crash must (1) be police-reported, (2) involve a harmful event resulting from the crash (such as property damage or personal injury), and (3) involve at least one passenger car, light truck, van, or sport utility vehicle in transport on a traffic-way that was towed from the scene due to damage. The gross vehicle weight rating should be less than 10,000 pounds. Crashes are selected so that a larger percentage of higher severity crashes are selected than lower severity crashes, but every motor vehicle crash that occurs within one of the PSUs where NASS-CDS data are collected and that meets these conditions has a chance of being selected for investigation. NHTSA selected the first stage of the current NASS-CDS sample in 1988 and the second stage in 1995 but selects the police accident reports weekly so that the evidence from the motor vehicle crashes that might be investigated is still intact and the memory of the individuals involved is still fresh. NHTSA contracts with two companies that use small teams of crash technicians located across the country to collect NASS-CDS data. These teams typically include a team leader, one or two crash technicians, and an assistant, and each team reports to one of two contractor-led control centers, called zone centers. NHTSA’s crash technicians collect over 600 data elements during their investigations, including information on the damage vehicles sustained, the crash forces involved, injuries to victims, and factors that caused those injuries. Those investigations generally involve inspecting the scene of a crash and the vehicles involved; interviewing the drivers and occupants involved, if possible; reviewing official medical reports detailing any injuries sustained; and reconstructing what happened during the crash, as shown in figure 3. The crash technicians coordinate with law enforcement agencies, hospitals, tow yard operators, repair garages, and the drivers and occupants involved in the crashes while performing their work, and the information they collect is subject to review by NHTSA. That information, in turn, is then made available to NHTSA and the public for research purposes. The number of NASS-CDS investigations NHTSA conducts each year varies, as shown in figure 4. Between 1988 and 2013, NHTSA conducted an average of about 4,700 NASS-CDS investigations each year. However, since 2009, the number of NASS-CDS investigations conducted has steadily decreased, and in 2013, only about 3,400 NASS- CDS investigations were conducted. According to NHTSA, factors that have contributed to this decline include the budget for NASS-CDS and rising costs. For example, funding for NASS-CDS has been flat-lined since 2010, whereas costs—including costs for labor, information technology, leases and fuel—have risen. NHTSA’s effort to redesign NASS-CDS is part of NHTSA’s larger Data Modernization Project, begun in 2012, which also affects NASS-GES and FARS. Specific to NASS-CDS, NHTSA’s Data Modernization Project involves the following: redesigning the NASS-CDS sample by reviewing the data elements that comprise the sample and the statistical methodology behind selecting the sample; upgrading the equipment and information technology that supports NASS-CDS to reduce redundancy, improve data quality, and enhance the experience of NASS users; and implementing a new sample to replace NASS-CDS. We found that the process NHTSA followed to redesign NASS-CDS is consistent with applicable government-wide standards and guidelines issued by OMB that apply to the development of survey concepts, methods, and design. OMB’s standards and guidelines specify the professional principles and practices that federal agencies are required to adhere to and the level of quality and effort expected when initiating a new survey or redesigning an existing survey. In the case of redesigning NASS-CDS, the OMB standards and guidelines that apply include recommended practices for the development of survey concepts, methods and design. As such, they highlight the importance of consulting with potential users to identify their requirements and expectations, including design elements in a sample to meet stated objectives, and testing a survey’s components prior to full-scale implementation. OMB’s standards and guidelines are not intended to substitute for the extensive existing literature on statistical and survey theory, methods, and operations. Further, these standards and guidelines specify that agencies should engage knowledgeable and experienced survey practitioners to effectively achieve the goals of OMB’s standards. While the process NHTSA has followed is consistent with applicable OMB standards and guidelines, NHTSA has not yet started implementing its new sample design. Accordingly, we were not able to assess its implementation efforts.