Effective Methods for Environmental Justice Assessment (2004) / Chapter Skim
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From page 133... ...
Increasing traffic volumes, flow speeds, or curb parking on such facilities thus can create important environmental justice concerns. STATE OF THE PRACTICE For transportation users, the safety benefits of facility improvements take the form of reductions in the rate of fatal, personal-injury, and property-damage-only (PDO)
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From page 134... ...
SELECTING AN APPROPRIATE METHOD OF ANALYSIS It is common practice to estimate the safety changes -- in the form of a reduction or increase in the number of crashes -- for any major street or highway project, including new road construction, reconstruction, capacity expansion, road maintenance, rehabilitation, and resurfacing, as well as safety and traffic flow improvements. It should not represent a major additional effort to compare the safety of collector facilities and local streets in areas that are within the daily activity space of minority populations and low-income populations.
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7. Pedestrian danger index Detailed Assess safety effects on pedestrians Project will increase the volume and/or speed of vehicular traffic in high pedestrian traffic areas, and detailed data on pedestrian exposure and injuries is available Medium Spreadsheet 8.
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Table 6-2 contains crash rates by functional class of road for 1997. The crash data in Table 6-2 are presented in rates of crashes per 100 million VMT.
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It presents clear, easily understandable results in the form of the differences in crash rates for each functional class of roadway. Overlaid on a GIS
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Comparison approach A comparison approach can partially overcome the limitations associated with using national data. This method entails comparing crash rates on a roadway where potential changes are being considered -- and other roadways comparable to it -- with existing roads in the region that are representative of the improved road.
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From page 139... ...
As discussed earlier in this chapter, roadways of a given standard are unlikely to be less safe in areas where members of protected populations live, work, or travel. The more likely environmental justice issue is whether particular facilities in such areas need to be upgraded because they currently have unacceptable crash rates.
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Variables used in regression model of crash costs Dependent variable • Natural log of number of crashes (fatal, injury, and PDO) per million VMT.
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Using the same crash data upon which the regression model is based, Table 6-5 shows the breakdown of crashes by type. We can use the crash cost data from Table 66 to construct a weighted estimate of the annual crash costs of the base and improved cases.
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With a crash incidence of 1.28 per million VMT, there are 112.1 crashes per year. With a weighted average crash cost of $96,184, the annual crash cost for the base case is $10.78 million.
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When to use. If a roadway through an area inhabited by protected populations is a candidate for upgrading, it is appropriate to evaluate the extent to which the safety of these populations would be affected as they move about.
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The most serious location factor is angled parking, and the best safety feature is a paved shoulder. The appropriate factor values are plugged into the BSI function, and an index value is obtained.
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–0.35 Center turn lane (scramble lane) –0.20 Paved shoulder –0.75 Grades, severe 0.50 Grades, moderate 0.20 Curves, frequent 0.35 Restricted sight distance 0.50 Numerous drives 0.25 Industrial land use 0.25 Commercial land use 0.25 Source: Epperson 1994, Table 2.
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He attributes this limited predictive ability to differences in bicycle use patterns and the diverse nature of cyclists. Regarding the latter point, Epperson suggests that the BSI is likely to more accurately predict crash rates of experienced cyclists than those of young children riding bicycles.
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The BCI consists of an equation into which the relevant values are inserted: AFAREAPKG SPDOLVCLVCLWBLWBLBCI +−+ +++−−−= 264.0506.0 022.00004.0002.0498.041.0966.067.3 where BL = presence of bicycle lane or paved shoulder (≥ 0.9 m.
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152 Table 6-11. Right turns factor (frt)
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These maps can be overlaid on maps indicating the common activity space of protected populations. Roadway suitability ratings can also be used to identify preferred cycling routes; these routes can be compared to the same activity space.
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It is there that pedestrian–motor vehicle conflicts are the most likely to occur. When changes are being considered for roadways that are frequently crossed by protected populations, environmental justice considerations dictate that every effort be made to make crossings as safe as possible.
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Estimating the pedestrian danger index values requires pedestrian crash data, population data, and pedestrian exposure data. If reliable data for each of the three variables are available at an appropriate level (i.e., community, neighborhood)
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If data can be obtained for comparable areas in several different communities, a more meaningful assessment can be made of the relative pedestrian danger in the area under study. The index values account for changes in population and pedestrian exposure; therefore, the index is a good measure of relative danger and can be used to compare areas with diverse land use and population density attributes.
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The benefit of the measurement is that, once calculated, it is an intuitive and concrete measurement that people can easily understand. It is important to present demographic information identifying protected populations along with the pedestrian danger index.
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p = portion of total population for each age range cpf = crossing potential factor for each age range, indicated in Table 6-15 Continuing our example, let the population density be 741 persons per square kilometer and the population age distribution be as shown in Table 6-16. Then the crossing potential can be obtained from Table 6-15.
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Crossing potential factor Population density Crossing potential Infant/Toddler (0-4 yrs) 0.07 0.42 741 22 Elementary (5-12 yrs)
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It is especially useful in estimating how great a change in barrier effects would result from a proposed transportation system project. Two key assumptions contained in the analysis influence the outcome: the crossing potential factor (i.e., the relative likelihood of risk-taking by age group)
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• What improvements or programs might improve walking and cycling conditions? For purposes of environmental justice assessment, it is necessary to collect information on the demographic characteristics of the survey respondents.
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In an environmental justice context, user demand and evaluation surveys can be carried out to estimate the specific effects a particular project would have on protected populations. These surveys also can be used to assess problem areas and the efficacy of possible improvements.
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Smaller analysis zones were created, and various demographic and transportation system factors that affect nonmotorized travel behavior were incorporated into the model. This article should be useful to planners and modelers who might want to incorporate nonmotorized travel into a conventional traffic model.
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From page 160... ...
2003. "Pedestrian Safety." Fact Sheet Library.
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From page 161... ...
165 Wellar, Barry.
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