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91 A P P E N D I X D State-Level MNCS Model Prediction vs. Performance The panels in this appendix compare the predicted number of fatalities for each state with the number actually experienced, computed as the ratio between observed and predicted. The MNCS (model not considering state) model was used for the purpose, because the goal was to compare how states differed from the prediction, in order to identify states that had more or fewer traffic fatalities than predicted by the model. In the panels, the horizontal line represents no difference from predicted. The dashed line represents the value obtained by dividing the observed number of traffic fatalities by the number of fatalities predicted by the MNCS model. Lines above the horizontal line represent a greater number than predicted, and those below represent fewer than predicted. The grayed band represents the 90% confidence interval of the ratio. Small states with relatively few traffic fatalities tended to have more volatility in their number of traffic fatalities, so the ratios were less stable. Predictions for larger states tended to be more stable and showed less fluctuation. For several states, the ratio was close to the horizontal line (of no difference), showing that the MCS model prediction was close to the outcome. In these states, the model explained most of the variation. These states included Alabama, Colorado, Florida, Mississippi, North Carolina, and Pennsylvania. In other states, the ratios were persistently less than 1. These states may have some features or programs that consistently resulted in a safer traffic environment. These states include Indiana, Massachusetts, Michigan, Minnesota, New York, Ohio, and Vermont. In other states, the dashed line was consistently above the horizontal line, indicating that the number of fatalities was persistently greater than predicted by the MNCS model. A comparison of states that had fewer traffic fatalities than predicted by the model, with the states that had more, would be useful to identify characteristics, programs, and interventions that contributed to the difference in safety environment.
92 Identification of Factors Contributing to the Decline of Traffic Fatalities in the United States from 2008 to 2012
State-Level MNCS Model Prediction vs. Performance 93
94 Identification of Factors Contributing to the Decline of Traffic Fatalities in the United States from 2008 to 2012
Abbreviations and acronyms used without definitions in TRB publications: A4A Airlines for America AAAE American Association of Airport Executives AASHO American Association of State Highway Officials AASHTO American Association of State Highway and Transportation Officials ACIâNA Airports Council InternationalâNorth America ACRP Airport Cooperative Research Program ADA Americans with Disabilities Act APTA American Public Transportation Association ASCE American Society of Civil Engineers ASME American Society of Mechanical Engineers ASTM American Society for Testing and Materials ATA American Trucking Associations CTAA Community Transportation Association of America CTBSSP Commercial Truck and Bus Safety Synthesis Program DHS Department of Homeland Security DOE Department of Energy EPA Environmental Protection Agency FAA Federal Aviation Administration FAST Fixing Americaâs Surface Transportation Act (2015) FHWA Federal Highway Administration FMCSA Federal Motor Carrier Safety Administration FRA Federal Railroad Administration FTA Federal Transit Administration HMCRP Hazardous Materials Cooperative Research Program IEEE Institute of Electrical and Electronics Engineers ISTEA Intermodal Surface Transportation Efficiency Act of 1991 ITE Institute of Transportation Engineers MAP-21 Moving Ahead for Progress in the 21st Century Act (2012) NASA National Aeronautics and Space Administration NASAO National Association of State Aviation Officials NCFRP National Cooperative Freight Research Program NCHRP National Cooperative Highway Research Program NHTSA National Highway Traffic Safety Administration NTSB National Transportation Safety Board PHMSA Pipeline and Hazardous Materials Safety Administration RITA Research and Innovative Technology Administration SAE Society of Automotive Engineers SAFETEA-LU Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (2005) TCRP Transit Cooperative Research Program TDC Transit Development Corporation TEA-21 Transportation Equity Act for the 21st Century (1998) TRB Transportation Research Board TSA Transportation Security Administration U.S. DOT United States Department of Transportation
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