Guidelines for the Application of Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities (2016) / Chapter Skim
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NCHRP 3-78b: Final Project Report April 2016 9 APPENDIX C: RISK MODEL DETAILS This appendix summarizes the risk modeling results for the combined data for TOPR-34 and NCHRP 3-78b. In order to create models to predict pedestrian risk rate, Stata was used to analyze data collected at roundabouts in states of Washington, Oregon, New York, Michigan, North Carolina, Maryland, Ohio, Wisconsin, and channelized turn lane locations in Colorado, North Carolina, Maryland and Arizona.
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From page 126... ...
NCHRP 3-78b: Final Project Report April 2016 Table 9-1: Variables of Interest in Risk Modeling Variable Description Value CTL Channelized Turn Lane Channelized Turn Lane=1, otherwise=0 RBTN Roundabout entry Roundabout entry=1, otherwise=0 RBTX Roundabout exit Roundabout exit =1, otherwise=0 NOISE Noise level experienced at the study location High=1, Low=0 SIGHT_D Whether the pedestrian sight distance was provided or not Sight distance provide=1, otherwise=0 LU Lane Utilization Unbalanced=1, balanced=0, OL_DEC Overlapping decision Points between yielding to pedestrian and finding gap in cross traffic Two decisions overlap=1, otherwise=0 XSPED_AVE Average pedestrian speed at crosswalk (>= 10mph) Continuous variable N2 Number of lanes Single lane =0, more than one lane=1 YR Average driver yield rate to pedestrians Continuous variable YUR Average yield utilization rate by blind pedestrians Continuous variable RDS Approach fastest path radius Continuous variable INT Intervention rates Continuous variable INTR Total of intervention and risky events rate Continuous variable Stata was used to analyze the data collected in order to create a model to predict the likelihood of intervention or intervention-risky crossings at an intersection by a blind pedestrian.
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NCHRP 3-78b: Final Project Report April 2016 Across the study locations, the data shows that the average intervention rate is 0.05 and the average intervention-risky rate is 0.17. This suggests that, on average, blind participants made "bad" crossing decisions which may have resulted in an intervention about 5% of the time.
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From page 128... ...
NCHRP 3-78b: Final Project Report April 2016 Table 9-3 Correlation Table for Variables n=52 INT INTR N2 NOISE SIGHT_D LU OL_DEC YR XSPD_AVE YUR RDS RBTN RBTX INT 1 INTR 0.8142*
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From page 129... ...
NCHRP 3-78b: Final Project Report April 2016 The correlation table revealed significant intercorrelation between independent variables. For example, XSPD_AVE (speed)
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From page 130... ...
NCHRP 3-78b: Final Project Report April 2016 The models were developed using a manual selection process informed by the results of the correlation analysis. Significantly associated independent variables were not included in the same model.
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NCHRP 3-78b: Final Project Report April 2016 Table 9-4 Single Variable Models for Intervention and Intervention-Risky Models Single Variable Intervention Models Single Variable Intervention-Risky Models Model 1a Coefficient Std.
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NCHRP 3-78b: Final Project Report April 2016 Table 9-4 shows the single variable models for intervention and intervention-risky predictions. Based on Table 9-4, the model with NOISE variable as the predictor has the highest R2 and adjusted R2 (0.48, 0.47 respectively for intervention and 0.33, 0.31 respectively for intervention-risky)
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NCHRP 3-78b: Final Project Report April 2016 Table 9-5 Intervention Models INT= NOISE YR XSPD_AVE SIGHT_D OLDEC N2 RBTX Constant Prob>F R2 Adj. R2 Model 1a 0.0773*
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NCHRP 3-78b: Final Project Report April 2016 Table 9-7 Intervention-Risky Models INT= NOISE YR XSPD_AVE SIGHT_D OLDEC N2 RBTX Constant Prob>F R2 Adj. R2 Model 1b 0.0773*
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NCHRP 3-78b: Final Project Report April 2016 9.4 Summary Multivariable linear regression models were generated to predict the rate that blind pedestrians may make bad crossing decisions that result in intervention events and intervention and risky events. Two separate models were generated to predict the intervention rates (associated with dangerous crossing decisions)
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From page 136... ...
NCHRP 3-78b: Final Project Report April 2016 Predicted Vs. Observed Intervention-Risky Rates Intervention-Risky Rate 45 Degree Line 0.7 0.6 Adj.
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