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Suggested Citation:"Appendix B - Descriptive Statistics." 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 84
Page 85
Suggested Citation:"Appendix B - Descriptive Statistics." 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 85
Page 86
Suggested Citation:"Appendix B - Descriptive Statistics." 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 86

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84 A P P E N D I X B Descriptive Statistics

Table B-1. Variables in MCS and MNCS models. Variable Units Non-missing observations Mean Median Std Dev Range 10th Pctl 90th Pctl TotalVMT Millions of miles 600 58,855.4 46,758.5 59,853.4 324,674.0 8,994.0 110,541.0 UrbanVMT Millions of miles 600 38,189.8 25,532.5 47,024.8 266,918.0 2,643.5 75,298.0 RuralVMT Millions of miles 600 20,665.6 17,419.0 15,586.2 85,131.0 4,033.5 38,043.0 ruralvmt_prop Proportion 600 0.44 0.44 0.19 0.91 0.19 0.72 cap_m_lag 1,000s dollars per highway mile (2013 dollars) 550 64.2 49.4 47.7 270.9 19.9 123.6 safe_total_m_lag 1,000s dollars per highway mile (2013 dollars) 550 10.8 8.2 10.0 58.1 2.5 23.5 gdp_cap Constant 2013 dollars 600 57,200.7 56,367.8 11,595.9 83,060.0 43,268.3 72,262.3 MedIncome Constant 2013 dollars 600 54,591.7 53,886.7 8,276.6 37,527.7 44,246.8 67,301.0 UnEmp_16_24 Percent 600 12.8 12.1 3.8 19.2 8.5 18.5 pump_price Constant 2013 dollars 600 2.81 2.84 0.6 2.88 1.95 3.68 Beer Gallons per capita 600 1.2 1.2 0.2 1.2 1.0 1.5 Wine Gallons per capita 600 0.4 0.3 0.2 0.9 0.2 0.6 BeltUse Percent 590 81.3 81.9 9.3 48.4 68.6 93.3 DUI_rating Index 600 19.3 19 3.3 17 15 24 Belt_rating Index 600 2.2 2 1.1 4 1 4 MC_hlmt_rating Index 600 2.7 2 1.2 4 2 4 post1991 Percent 600 93.4 95.3 4.7 15.4 86.9 97.6

Table B-2. Variables in change model. Variable Non-missing observations Mean Median Std Dev Range 10th Pctl 90th Pctl TotalVMT_chng 550 0.00622 0.00789 0.02562 0.35682 -0.02135 0.03286 Ruralvmt_prop_chng 550 -0.01939 -0.00265 0.07630 0.89543 -0.05241 0.01552 pump_price_chng 550 0.05467 0.09493 0.12895 0.56582 -0.10027 0.17155 gdp_cap_chng 550 -0.01966 -0.01713 0.06465 1.40280 -0.05227 0.01856 MedIncome_chng 550 -0.00553 -0.00444 0.02945 0.21803 -0.04311 0.02765 UnEmp_16_24_chng 550 0.03487 0.02442 0.19197 1.58067 -0.18368 0.30060 cap_m_chng_lag 500 0.00980 0.00442 0.19744 1.88702 -0.21202 0.23149 safe_total_m_chng_lag 500 0.02805 0.03784 0.31743 3.83360 -0.21989 0.29174 BeltUse_chng 537 0.01669 0.01056 0.04165 0.49134 -0.02260 0.06047 DUI_rating_chng 550 0.01356 0.00000 0.04602 0.47000 0.00000 0.05268 MC_hlmt_rating_chng 550 0.00000 0.00000 0.04184 1.38629 0.00000 0.00000 Beer_chng 550 -0.00591 -0.00755 0.03412 0.36229 -0.04078 0.02765 Wine_chng 550 0.02910 0.02740 0.05024 0.40705 -0.00552 0.08004 Post1991_chng 550 0.01556 0.01049 0.01463 0.04889 0.00308 0.02979

Next: Appendix C - State-Specific Parameters for the MCS Model »
Identification of Factors Contributing to the Decline of Traffic Fatalities in the United States from 2008 to 2012 Get This Book
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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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