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Identification of Factors Contributing to the Decline of Traffic Fatalities in the United States from 2008 to 2012 (2020)

Chapter: Appendix D - State-Level MNCS Model Prediction vs. Performance

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Page 91
Suggested Citation:"Appendix D - State-Level MNCS Model Prediction vs. Performance." National Academies of Sciences, Engineering, and Medicine. 2020. Identification of Factors Contributing to the Decline of Traffic Fatalities in the United States from 2008 to 2012. Washington, DC: The National Academies Press. doi: 10.17226/25590.
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Suggested Citation:"Appendix D - State-Level MNCS Model Prediction vs. Performance." National Academies of Sciences, Engineering, and Medicine. 2020. Identification of Factors Contributing to the Decline of Traffic Fatalities in the United States from 2008 to 2012. Washington, DC: The National Academies Press. doi: 10.17226/25590.
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Page 92
Page 93
Suggested Citation:"Appendix D - State-Level MNCS Model Prediction vs. Performance." National Academies of Sciences, Engineering, and Medicine. 2020. Identification of Factors Contributing to the Decline of Traffic Fatalities in the United States from 2008 to 2012. Washington, DC: The National Academies Press. doi: 10.17226/25590.
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Page 93
Page 94
Suggested Citation:"Appendix D - State-Level MNCS Model Prediction vs. Performance." National Academies of Sciences, Engineering, and Medicine. 2020. Identification of Factors Contributing to the Decline of Traffic Fatalities in the United States from 2008 to 2012. Washington, DC: The National Academies Press. doi: 10.17226/25590.
×
Page 94
Page 95
Suggested Citation:"Appendix D - State-Level MNCS Model Prediction vs. Performance." National Academies of Sciences, Engineering, and Medicine. 2020. Identification of Factors Contributing to the Decline of Traffic Fatalities in the United States from 2008 to 2012. Washington, DC: The National Academies Press. doi: 10.17226/25590.
×
Page 95
Page 96
Suggested Citation:"Appendix D - State-Level MNCS Model Prediction vs. Performance." National Academies of Sciences, Engineering, and Medicine. 2020. Identification of Factors Contributing to the Decline of Traffic Fatalities in the United States from 2008 to 2012. Washington, DC: The National Academies Press. doi: 10.17226/25590.
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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 ACI–NA Airports Council International–North 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 America’s 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

TRA N SPO RTATIO N RESEA RCH BO A RD 500 Fifth Street, N W W ashington, D C 20001 A D D RESS SERV ICE REQ U ESTED ISBN 978-0-309-48111-3 9 7 8 0 3 0 9 4 8 1 1 1 3 9 0 0 0 0 N O N -PR O FIT O R G . U .S. PO STA G E PA ID C O LU M B IA , M D PER M IT N O . 88

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Between 2005 and 2011, the number of traffic fatalities in the U.S. declined by 11,031, from 43,510 in 2005 to 32,479 in 2011. This decline amounted to a reduction in traffic-related deaths of 25.4 percent, by far the greatest decline over a comparable period in the last 30 years.

Historically, significant drops in traffic fatalities over a short period of time have coincided with economic recessions. Longer recessions have coincided with deeper declines in the number of traffic fatalities. This TRB National Cooperative Highway Research Program's NCHRP Research Report 928: Identification of Factors Contributing to the Decline of Traffic Fatalities in the United States from 2008 to 2012 provides an analysis that identifies the specific factors in the economic decline that affected fatal crash risk, while taking into account the long-term factors that determine the level of traffic safety.

A key insight into the analysis of the factors that produced the sharp drop in traffic fatalities was that the young contributed disproportionately to the drop-off in traffic fatalities. Of the reduction in traffic fatalities from 2007 to 2011, people 25-years-old and younger accounted for nearly 48 percent of the drop, though they were only about 28 percent of total traffic fatalities prior to the decline. Traffic deaths among people 25-years-old and younger dropped substantially more than other groups. Young drivers are known to be a high-risk group and can be readily identified in the crash data. Other high-risk groups also likely contributed to the decline but they cannot be identified as well as age can.

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