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Data Analysis (Task 2)
Pages 22-47

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From page 22...
... Second, they used data from Minnesota, North Carolina, and Washington to better understand design and environmental factors that best predict crash incidence. Third, the research team used the same data to analyze crash severity by rural road type and rural county type for five states.
From page 23...
... As described later, they divide this count of fatal crashes by VMT to calculate crash rates by county and smooth the number of fatalities (which vary from year to year) by averaging crash counts over a five-year period, which is a typical practice in safety analysis.
From page 24...
... More importantly, researchers at the University of Utah, where NEMSIS is hosted, were unable to provide geographic detail on NEMSIS data which limits its usefulness when studying differences in crash patterns or EMS response by county type. Regional Integrated Transportation Information System To assist transportation planning agencies with setting targets, programming projects, and measuring and reporting progress, USDOT established the Regional Integrated Transportation Information System (RITIS)
From page 25...
... Individual State Data Sources Before gaining access to the state-level HSIS data described above, the research team collected crash data directly from several states to determine their applicability for this analysis. The investigated states include the following: • Alabama: Crash data from 2015-2019, including county, crash severity, date/time, location, and functional class.
From page 26...
... While using only three to five states for portions of the analysis limits its generalizability, the research team felt that Alabama, Alaska, Minnesota, North Carolina, and Washington together offer a variety of county types, road types, and other characteristics that will allow researchers and practitioners to draw meaningful conclusions on factors contributing to rural road safety. Although Alaska is different from the lower 48 states in many respects, its uniqueness makes it an important part of rural safety research.
From page 27...
... Alaska, Minnesota, and Washington State County Types
From page 28...
... 4,903,190 731,550 5,639,630 10,488,084 7,614,890 Safety Data Source Alabama DOT Alaska DOT HSIS HSIS HSIS Years of Safety Data Used 2015-2019 2015-2017 2013-2015 2016-2018 2016-2018 Total Lane-Miles N/A N/A 293,250 171,808 18,440 Average Annual Crashes 156,435 7,160 89,900 237,529 62,760 Crash Frequency and Incidence The first step in the analysis was to determine crash incidence using the rural road safety classification system. This involved calculating the average annual number of crashes per road mile for each rural county type and rural road type.
From page 29...
... The analysis of Alaska crash data showed noticeable differences among rural road types and rural county types. In Alaska's sole Agriculture and Extraction county, in the far north region of the state, most crashes occur on either minor collectors or local roads (Table 10)
From page 30...
... Crashes per Million VMT by Rural County and Rural Road Type in Minnesota, 2013-2015 County Type Interstate Other Principals & Arterials Minor Arterials Major Collector Minor Collector Local Road Agriculture & Extraction 0.51 0.44 0.14 0.06 0.03 Destination 13.27 0.99 2.65 0.90 0.27 0.17 Fringe 11.99 1.31 1.04 0.66 0.33 0.10 Micropolitan 13.96 1.46 1.25 0.72 0.46 0.21 Older-age 0.81 1.04 0.53 0.30 0.07 Remote 21.99 1.11 0.45 0.24 0.08 0.03 Rural Towns 8.37 0.73 0.71 0.42 0.15 0.08 Tribal 0.39 0.41 0.32 0.12 0.06 Source: 2013-2015 Minnesota HSIS crash data averaged over the three-year period. As in Alabama, crashes in North Carolina commonly occur on other principals and arterials and minor arterials (Table 13)
From page 31...
... Table 14. Crashes per Million VMT by Rural County and Rural Road Type in North Carolina, 20162018 County Type Interstate Freeways & Expressways Other Principals & Arterials Minor Arterials Major Collector Minor Collector Local Road Destination 8.87 3.11 3.12 1.81 1.09 0.87 0.65 Fringe 8.58 2.37 2.94 1.53 1.02 0.80 0.54 Micropolitan 12.04 1.70 2.08 1.50 0.98 0.89 0.54 Older-age 5.25 3.05 1.49 1.31 1.09 0.80 0.46 Remote 9.03 2.37 1.52 1.21 0.66 0.48 Rural Towns 2.72 0.77 0.86 0.46 0.19 Tribal 15.11 1.07 NA 0.53 0.28 0.29 Source: 2016-2018 North Carolina HSIS crash data averaged over the three-year period.
From page 32...
... Crashes per Million VMT by Rural County and Rural Road Type in Washington, 20162018 County Type Interstate Other Freeways & Expressways Other Principals & Arterials Minor Arterials Major Collector Minor Collector Local Road Agric. & Extraction 0.03 1.19 NA Destination 1.77 1.90 1.77 1.04 Fringe 2.87 1.95 0.73 1.11 Micropolitan 3.75 1.71 1.65 1.42 0.98 Older-age 2.29 1.35 1.75 0.88 Remote 6.22 1.12 0.82 0.49 0.46 Tribal NA Source: 2013-2015 Minnesota HSIS crash data averaged over the three-year period.
From page 33...
... In micropolitan counties, crash incidence is positively correlated with number of lanes, lane width, and the presence of an urban area or cluster. Destination counties in Washington and Minnesota are unique from other rural county types in that crash incidence is negatively correlated with number of lanes, lane width, and location within an urban area or cluster.
From page 34...
... Percent of Crashes by Rural Road Type and Crash Severity in Alabama, 2015-2019 Road Type Fatality Injury No Injury Interstates 1.2% 19.1% 79.7% Other Principals & Arterials 0.8% 24.7% 74.5% Minor Arterials 1.0% 26.4% 72.6% Major Collectors 1.5% 29.1% 69.3% Minor Collectors 2.1% 33.4% 64.5% Local Roads 0.8% 23.4% 75.8% Source: 2015-2019 Alabama Integrated Crash Data from the Alabama DOT averaged over the five-year period. Note: In Alabama, there are no roads classified as Other Freeways and Expressways.
From page 35...
... Percent of Crashes by Rural Road Type and Crash Severity in Minnesota, 2013-2015 Road Type Fatality Injury No Injury Interstates 0.2% 24.2% 75.6% Other Principal & Arterials 0.6% 29.7% 69.7% Minor Arterials 0.4% 30.5% 69.0% Major Collectors 0.7% 30.5% 68.7% Minor Collectors 2.0% 38.5% 59.4% Local Roads 0.3% 24.7% 74.9% Source: 2013-2015 Minnesota HSIS crash data averaged over the three-year period. Note: In Minnesota, there are no roads classified as Other Freeways and Expressways.
From page 36...
... Percent of Crashes by Rural Road Type and Crash Severity in Washington, 2016-2018 Road Type Fatality Injury No Injury Interstates 0.4% 25.3% 74.3% Other Freeways & Expressways 0.5% 28.9% 70.5% Other Principals & Arterials 0.4% 31.2% 68.4% Minor Arterials 0.7% 31.4% 67.9% Major Collectors 0.9% 32.9% 66.1% Minor Collectors 0% 26.3% 73.7% Local Roads 0% 24.0% 75.9% Source: 2016-2018 Washington HSIS crash data averaged over the three-year period. Crash Severity by County Type Table 22 shows crash severity by rural county type in Alabama.
From page 37...
... Table 23. Percent of Crashes by Rural County Type and Crash Severity in Alaska, 2015-2017 County Type Fatality Injury No Injury Agriculture & Extraction 1.9% 52.9% 45.2% Destination 1.3% 30.7% 67.9% Metropolitan 0.4% 31.9% 67.6% Micropolitan 0.8% 40.8% 58.4% Remote 3.2% 32.4% 64.3% Tribal 1.7% 33.7% 64.6% Source: 2015-2017 Alaska DOT and Public Facilities Highway Safety Office crash data averaged over the 3-year period.
From page 38...
... Percent of Crashes by County Type and Crash Severity in North Carolina, 2016-2018 County Type Fatality Injury No Injury Destination 0.6% 26.8% 72.6% Fringe 0.6% 32.8% 66.6% Metropolitan 0.6% 28.5% 70.9% Micropolitan 0.6% 29.3% 70.1% Older-age 0.9% 28.6% 70.5% Remote 1.1% 30.3% 68.5% Rural Towns 2.1% 25.9% 71.9% Tribal 1.2% 33.4% 65.4% Source: 2016-2018 North Carolina HSIS crash data averaged over the three-year period. Note: In North Carolina, there are no counties classified as Agriculture and Extraction.
From page 39...
... . In remote counties, 28.9% of fatal crashes involve a drunk driver -- the highest among rural county types.
From page 40...
... The analysis showed that while speeding may not be a predictor of overall crash likelihood in destination counties, fatal crashes caused by speeding are still more likely than in other rural county types.
From page 41...
... This includes seatbelt use for vehicle occupants and helmet use for motorcyclists. In all rural county types, vehicle occupants and motorcyclists killed in fatal crashes are less likely to be restrained relative to metropolitan counties (Figure 8)
From page 42...
... Across all measures, remote counties and agriculture and extraction counties exceed the national average for percent of fatal crashes involving a risky behavior. Crash Reductions Task 4 of this research included case studies of jurisdictions that have experienced rural road safety improvements.
From page 43...
... The Special Rule also instructs states to calculate the fatality rate for rural major and minor collectors and rural local roads using data from the HPMS and FARS. The research team recreated the Special Rule analysis by calculating the change in average annual crash fatalities on a county basis between the periods 2012-2016 and 2014-2018 using all rural U.S.
From page 44...
... 44 Figure 10: Top Five Rural Counties Within Each NHTSA Region by Decline in Annual Rural Fatal Crashes per 100 Million VMT
From page 45...
... In remote counties, higher speeds do lead to higher crash incidence. – Destination counties are unique among other rural county types, suggesting that visitors play some role in safety outcomes.
From page 46...
... • Micropolitan – Micropolitan counties behave similarly to metropolitan counties regarding the factors that influence crash incidence -- i.e., number of lanes, lane widths, and presence of urban areas or clusters. This suggests that behavioral countermeasures designed for rural areas may not be as effective in Micropolitan counties as they are in other rural county types.
From page 47...
... Only Minor Arterials showed a statistically significant relationship.) • In three of the states analyzed -- Alabama, Minnesota, and North Carolina -- Minor Collectors stand out as road type where fatal crashes and crashes involving injuries but no fatalities are most common.


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