Design Guidance for Channelized Right-Turn Lanes (2014) / Chapter Skim
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Chapter 5. Safety Analysis of Channelized Right Turns This chapter presents the results of a safety analysis of channelized right-turn lanes.
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channelized right-turn lane on one approach; others had a channelized right-turn lane on two or more approaches. Therefore, the analysis was conducted at the intersection approach rather than at the intersection level.
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multiple-vehicle right-turn crash involving the intersection approach being analyzed by definition includes a right-turning vehicle (Movement 3)
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The following sections present the statistical analysis results, separately for each analysis model. Each section presents the following information: 1.
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Figure 29. Summary of Analysis Model 1 Inputs and Criteria 65
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• Vol1 always represents the right-turning MV volume (i.e., Vol1 corresponds to vehicle Movement 3, indicated in red) • Vol2 always represents the sum of the remaining MV volumes of the same direction included in the model (i.e., Vol2 corresponds to the sum of vehicle Movements 1 and 2)
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Table 15. Regression Results for Motor-Vehicle Crash Models -- Analysis Model 1 Parametera Regression coefficientsb Type 3 p-value Parameter significant at 90% confidence level?
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Using Equation (1) and the regression coefficients shown in Table 15, yearly MV crash counts were predicted for all three approach types.
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Figure 30. Summary of Analysis Model 2 Inputs and Criteria 69
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Table 17. Mean and Median Motor-Vehicle Volumes by Intersection Type -- Analysis Model 2 Intersection approach type Number of approaches Mean MV volumes (24-hr counts)
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Table 19. Regression Results for Motor-Vehicle Crash Models -- Analysis Model 2 Parametera Regression coefficientsb Type 3 p-value Parameter significant at 90% confidence level?
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5.3.3 Analysis Model 3 Results Analysis Model 3 focuses on those vehicle maneuvers more likely to conflict with the rightturning vehicle. This analysis includes the right-turn movement (Movement 3)
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Figure 31. Summary of Analysis Model 3 Inputs and Criteria 73
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Table 23. Regression Results for Motor-Vehicle Crash Models -- Analysis Model 3 Parametera Regression coefficientsb Type 3 p-value Parameter significant at 90% confidence level?
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total crash predictions tend to show that CRT and STR approaches have similar safety performance (0.162 crashes per year per approach based on mean CRT volumes or 0.157 crashes per year per approach based on median CRT volumes)
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Figure 32. Summary of Analysis Model 4 Inputs and Criteria 76
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The regression results for the total and FI models are summarized in Table 27. The algorithm to estimate the regression coefficients for the FI crash model did not converge, therefore no model for FI crashes for Analysis Model 4 is available.
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Table 28. Contrast Results for Motor-Vehicle Crash Models -- Analysis Model 4 Comparison Crash rate lower at CRT?
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Figure 33. Summary of Analysis Model 5 Inputs and Criteria 79
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Volume statistics (mean and median) corresponding to Analysis Model 5 are shown in Tables 30, where Vol1 and Vol2 are defined in Figure 33.
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Table 32. Regression Results for Motor-Vehicle Crash Models -- Analysis Model 5 Parametera Regression coefficientsb Type 3 p-value Parameter significant at 90% confidence level?
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5.3.6 Analysis Models 6 Results Analysis Models 6a, 6b, and 6c are similar to Analysis Model 5, except that the left-turn movement (Movement 1) is excluded from the analysis.
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Figure 34. Summary of Analysis Model 6 Inputs and Criteria 83
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Table 35. Seven (7)
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Table 36. Regression Results for Motor-Vehicle Crash Models -- Analysis Model 6 (Continued)
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• Although the overall effect of the right-turn treatment was statistically significant (for FI crashes) in Analysis Model 6a, neither one-to-one comparison was statistically significant at the 90 percent confidence level (p = 0.59 for CRT vs.
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Table 38. Yearly Motor-Vehicle Crash Predictions -- Analysis Models 6 Intersection approach type Yearly crash predictions per approach At mean CRT volumes At median CRT volumes Total motor-vehicle crashes -- Analysis Model 6a STR 0.057 0.048 RTL 0.059 0.050 CRT 0.081 0.069 Fatal-and-injury motor-vehicle crashes -- Analysis Model 6a STR 0.010 0.008 RTL 0.011 0.009 CRT 0.012 0.010 Total motor-vehicle crashes -- Analysis Model 6b STR 0.039 0.032 RTL 0.041 0.033 CRT 0.066 0.054 Fatal-and-injury motor-vehicle crashes -- Analysis Model 6b STR 0.008 0.006 RTL 0.011 0.009 CRT 0.012 0.010 Total motor-vehicle crashes -- Analysis Model 6c STR 0.039 0.033 RTL 0.043 0.036 CRT 0.061 0.051 Fatal-and-injury motor-vehicle crashes -- Analysis Model 6c STR 0.008 0.006 RTL 0.011 0.009 CRT 0.011 0.009 While the overall analysis of treatment type suggests that CRT approaches may experience more rear-end and sideswipe crashes between the right-turning vehicle and either (1)
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Figure 35. Summary of Analysis Model 7 Inputs and Criteria 88
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pedestrian movements of interest. Movement 13 consists of the pedestrian crossing the approach that the right-turning vehicle turns from (in this case, Approach 1)
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Table 41. Regression Results for Pedestrian Crash Models -- Analysis Model 7 Parametera Regression coefficientsb Type 3 p-value Parameter significant at 90% confidence level?
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Table 43. Yearly Pedestrian Crash Predictions -- Analysis Model 7 Intersection approach type Yearly crash predictions per approach At mean CRT volumes At median CRT volumes Total pedestrian crashes -- Analysis Model 7 STR 0.025 0.017 RTL 0.043 0.029 CRT 0.024 0.016 Fatal-and-injury pedestrian crashes -- Analysis Model 7 STR 0.024 0.016 RTL 0.043 0.029 CRT 0.023 0.015 The yearly pedestrian crash predictions for CRT and STR approaches are similar (0.024 total crashes per CRT approach vs.
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(0.162 total crashes per year, on average, for both approach types) , while the crash frequencies for RTL approaches were slightly higher (0.2 total crashes per year, on average, per approach)
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