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Pages 19-34

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From page 19...
... 19   Encroachment Variable Distributions and Marginal Probabilities NCHRP Web-Only Document 341 Crash Database The research team used the crash database from NCHRP Web-Only Document 341 to develop univariate distributions for the encroachment parameters in the simulation matrix (3)
From page 20...
... 20 Development of Clear Recovery Area Guidelines for the selected encroachment parameters for both 2U and 4D roadways. These distributions were used to determine conditional probabilities for the values of the variables used in the simulation matrix.
From page 21...
... Encroachment Variable Distributions and Marginal Probabilities 21   Figure 7. Weighted distribution of encroachment speeds.
From page 22...
... 22 Development of Clear Recovery Area Guidelines or equal to 30 mph and less than 40 mph. The 45-mph bin represents all crashes with a reported encroachment speed greater or equal to 40 mph and less than 50 mph.
From page 23...
... Encroachment Variable Distributions and Marginal Probabilities 23   use in the simulation matrix. The research team considered different sets of encroachment angle values and concluded those presented in Table 8 provided a reasonably balanced set of marginal probabilities across both 2U and 4D roadways.
From page 24...
... 24 Development of Clear Recovery Area Guidelines 10 ,0 00 20 ,0 00 30 ,0 00 40 ,0 00 0 Fr eq ue nc y Figure 9. Weighted distribution of sideslip angles (right-side departures)
From page 25...
... Encroachment Variable Distributions and Marginal Probabilities 25   A clear observation is that a large proportion of the sideslip angles are small (75% of the data has absolute sideslip angles smaller than 11.08 degrees)
From page 26...
... 26 Development of Clear Recovery Area Guidelines encroachments that would result for each value. For example, Figure 12 indicates that 82% of the sideslip angles are smaller than or equal to 15 degrees.
From page 27...
... Encroachment Variable Distributions and Marginal Probabilities 27   for each driver input category. Additional data elements were extracted from the NASS-CDS database and merged with the NCHRP Web-Only Document 341 database (3)
From page 28...
... 28 Development of Clear Recovery Area Guidelines 2U and 4D roadways, respectively. This percentage of no driver response is not consistent with driver input responses derived from the older database in NCHRP Report 665 (16)
From page 29...
... Encroachment Variable Distributions and Marginal Probabilities 29   The maneuver distributions associated with crash events that occurred greater than 10 ft off the roadway are shown in Figure 18 and Figure 19 for 2U and 4D roadways, respectively. Comparing Figure 18 and Figure 19 with the respective distributions in Figure 14 and Figure 15, a significant drop in the percentage of no driver response is observed for both 2U and 4D roadways.
From page 30...
... 30 Development of Clear Recovery Area Guidelines Figure 18. Distribution of driver input for objects struck greater than 10 ft off roadway (2U roadways)
From page 31...
... Encroachment Variable Distributions and Marginal Probabilities 31   Vehicle Probability Matrix The researchers analyzed vehicle sales data to determine the marginal probability for each vehicle platform category of interest and selected a representative vehicle from each class for use in the encroachment simulation analyses. The researchers used 2019 U.S.
From page 32...
... 32 Development of Clear Recovery Area Guidelines The Insurance Institute for Highway Safety (IIHS) has three classifications for pickups based on carrying capacity and curb weight as follows: • Small (P1)
From page 33...
... Encroachment Variable Distributions and Marginal Probabilities 33   adequately represent this category in the simulations. Of particular note is the rapidly growing vehicle category that is being referred to by the manufacturers as either CUV or crossover.
From page 34...
... 34 Development of Clear Recovery Area Guidelines Figure 22. Sales-based probabilities for the selected vehicle categories.

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