The Relative Risks of School Travel A National Perspective and Guidance for Local Community Risk Assessment -- Special Report 269 (2002) / Chapter Skim
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5 Application of Risk Estimates: Illustrative Scenarios
5 Application of Risk Estimates: Illustrative Scenarios
Pages 145-158
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From page 145... ...
The three scenarios presented here illustrate the application of all four risk measures presented in Chapter 3: injuries and fatalities per 100 million studentmiles and per 100 million student trips. The first scenario examines the effects of changing the minimum school bus pickup distances for a suburban elementary school and employs the per student-mile risk measures.
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From page 146... ...
No School Bus Service Less than 1 60 30 10 11.5 50 35 15 1.52 36 25 37 2 23 22 16 60 2 34 5 10 82 3 45 5 92 3 56 97 3 67 97 3 78 97 3 89 97 3 910 97 3 146
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From page 147... ...
To compute total distance traveled by students living at the various distances and taking the different modes, an average trip-length multiplier was used. It was assumed that a student walking to school would take a fairly direct path and would travel a distance closest to the direct distance; the multiplier for a walking student was estimated to be 1.25 times the direct distance.
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From page 148... ...
Teen 0.2 0.4 0.3 0.3 0.2 0.2 0.1 0.1 0.0 2 1 Driver 4.8 3.6 6.6 15.0 14.6 11.0 9.0 7.0 5.0 3.0 1.0 81 23 Adult Driver 1,283 Distance Pickup Bus 8.3 9.2 18.4 17.6 16.2 13.3 10.3 7.4 4.4 1.5 Bus 34 107 School School Minimum 14.3 4.8 1.4 2.8 9 23 1-Mile Bicycling 3,463 for Measures 28.5 7.1 1.4 0.9 38 15 Risk Mode Walking Mode 6,413 and Travel Transportation 1: Transportation by by Year per Scenario Students of 5-2 school 1 Miles school 1 from than students than Number 11.5 23 34 45 56 67 78 89 910 students from Less 1.52 of Student Less TABLE (a) Miles Total % (b)
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From page 149... ...
1 0.11 61 0.0006 12 177 506 614 668 668 614 506 344 128 4,227 0.13 36 02 0.0005 9 2,405 6,202 20,250 27,641 26,730 26,730 24,570 20,250 13,770 5,130 174,960 0.04 6 0.0003 5 59 6,546 10,129 28,941 38,698 45,998 45,998 42,281 34,847 23,696 8,828 285,961 2 0.29 44 0.0023 43 2,886 1,196 3,417 10,962 3 0.09 14 0.0017 32 0.659 0.0054 4,008 1,107 1,055 12,582 year year per per /year Measures injuries fatalities injuries fatalities 11.5 23 34 45 56 67 78 89 910 miles/year of of 1.52 miles Risk Injuries % Fatalities/year % Total Total Total % (c)
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From page 150... ...
Driver 0.2 0.4 0.3 0.3 0.2 0.2 0.1 0.1 0.0 2 1 Teen Driver 4.8 3.6 6.9 15.0 14.6 11.0 9.0 7.0 5.0 3.0 1.0 81 32 Distance 1,283 Adult Pickup Bus Bus 18.4 17.6 16.2 13.3 10.3 7.4 4.4 1.5 89 36 School School Minimum 2-Mile 14.3 8.3 4.9 2.8 30 12 Bicycling 3,463 with Measures 28.5 11.9 6.8 0.9 48 19 Risk Mode Walking Mode 6,413 and Travel Transportation 1: Transportation by by Year per Scenario Students of 5-3 school 1 Miles school 1 from than students than Number 23 34 45 56 67 78 89 910 students from Less 11.5 1.52 of Student Less TABLE (a) Miles Total % (b)
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From page 151... ...
1 0.11 177 506 614 668 668 614 506 344 128 31 0.0006 9 4,227 0.13 37 61 0.0005 6 2,405 6,556 20,250 27,641 26,730 26,730 24,570 20,250 13,770 5,130 175,314 0.04 4 0.0003 4 56 28,941 38,698 45,998 45,998 42,281 34,847 23,696 8,828 269,286 3 0.42 50 0.0034 46 5,050 4,146 3,417 16,076 4 0.14 17 0.0026 36 0.842 0.007 6,680 5,316 1,055 19,463 year year per per Measures injuries fatalities injuries fatalities 11.5 23 34 45 56 67 78 89 910 miles/year of of 1.52 miles Risk Injuries/year % Fatalities/year % Total Total Total % (c)
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From page 152... ...
Student Miles per Year by Transportation Mode Miles from school Less than 1 6,413 3,463 1,283 11.5 6,680 5,050 2,405 1.52 5,316 3,987 6,556 354 23 9,281 7,290 30,375 1,013 34 2,559 5,528 50,369 1,843 45 3,007 61,479 2,005 56 64,820 2,005 67 59,582 1,843 78 49,106 1,519 89 33,392 1,033 910 12,440 385 Total miles/ year 30,248 28,325 371,807 11,998 % miles 7 7 86 3 (c) Risk Measures Injuries/year 0.22 0.74 0.29 0.31 % of injuries 14 48 0 18 20 Fatalities/year 0.0041 0.0060 0.0010 0.0018 % of fatalities 32 46 0 8 14 Total injuries per year 1.555 Total fatalities per year 0.013
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From page 153... ...
This impact can be seen in Figure 5-1: increasing the minimum pickup distance from 1 to 2 miles would increase the student risk by more than 27 percent, while eliminating school bus service would more than double the student risk as compared with a 1-mile pickup policy. Scenario 2: Adding School Bus Service for Students Attending After-School Activities A hypothetical suburban middle school with 750 students was used to demonstrate how additional after-school bus service might affect total transportation 1.8 0.018 Injuries/yr 1.6 0.016 Fatalities/yr 1.4 0.014 Fatalities 1.2 0.012 year 1.0 0.010 per per 0.8 0.008 year Injuries 0.6 0.006 0.4 0.004 0.2 0.002 0.0 0.000 1 Mile 2 Miles No Bus Minimum Pickup Distance FIGURE 5-1 Scenario 1: effects of minimum school bus pickup distances on student injuries and fatalities per year.
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From page 154... ...
. Therefore, the calculation for bicycle injuries is TABLE 5-5 Scenario 2: Effects of Adding Bus Service for Students Participating in After-School Activities, Showing Afternoon Trips for All Students (Students 1113 Years Old)
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From page 155... ...
Of all the scenarios, this one has the greatest negative effect on school travel safety. If the school encourages student driving by doubling the number of student parking spaces, the risks faced by the student population increase considerably.
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From page 156... ...
30 360 1.38 0.0152 Total for age group 100 1,200 4.02 0.025 Years between events 0.2 39.4 School total 7.92 0.05 Years between events for school 0.13 50.56 (b) 600 Student Parking Spaces 1415 Years Old School bus 25 300 0.15 0.0003 Other bus 5 60 0.01 0.0000 Passenger vehicle (adult driver)
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From page 157... ...
CONCLUSIONS The scenarios presented in this chapter illustrate how the risk measures from Chapter 3 can be used with local school information to complete an assessment of the risks associated with different school travel policies. In these examples, adding after-school bus service or changing the minimum school bus pickup distance can easily increase or decrease injury and fatality risks by 20 to 50 percent or more.
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From page 158... ...
Unfortunately, the data available to the committee were not sufficient to determine the extent of risk reduction associated with these and other risk mitigation options. Nevertheless, before adopting policies that shift the distribution of travel among modes, policy makers would be well advised to consider the trade-offs involved.
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