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From page 136...
... 136 Chapter 6. Development of Models for Use in HSM Crash Prediction Methods: Five-Leg Intersections This section describes the development of crash predictive methods for five-leg intersections and presents the final models recommended for incorporation in the second edition of the HSM.
From page 137...
... 137 Visual investigation was essential to correct misclassifications of four-leg and six-leg intersections as five-leg intersections in the initial dataset. This was in part due to link-node roadway representations that showed five links approaching a given node.
From page 138...
... 138 Table 56 lists the intersection attributes collected (and respective definitions and permitted values) for five-leg intersections.
From page 139...
... 139 Therefore, the total number of intersections available for model development was 76, including 39 intersections from Ohio, 13 from Illinois, 13 from Massachusetts, and 11 from Minnesota. Definitions of intersection and intersection-related crashes from existing HSM intersection predictive methods were used for this study.
From page 140...
... 140 Table 58. Major-, minor-, and fifth-road AADT statistics at urban, five-leg signalized intersections State Date Range Number of Sites Number of SiteYears Major Road AADT (veh/day)
From page 141...
... 141 Crash Counts All 76 intersections experienced crashes during the study period. The average number of single- and MV crashes per intersection over the 5-year study period was 35.2 crashes, and the average number of nonmotorized (i.e., vehicle-pedestrian plus vehicle-bicycle)
From page 142...
... 142 Table 59. All crashes combined, single- and MV, and pedestrian and bicycle crash counts by crash severity -- urban, five-leg signalized intersections State Date Range Number of Sites Number of SiteYears Time of Day All Crashes Combined SV Crashes Multiple-Vehicle Crashes Pedestrian Crashes Bicycle Crashes Total FI PDO Total FI PDO Total FI PDO FI FI OH 2009-2013 39 195 All 1,434 428 1,006 37 10 27 1,351 372 979 27 19 Night 322 109 213 15 4 11 294 92 202 8 5 MA 2009-2013 13 65 All 327 99 228 21 5 16 278 66 212 15 13 Night 88 30 58 7 4 3 72 17 55 7 2 IL 2009-2013 13 65 All 867 265 602 33 11 22 745 165 580 42 47 Night 222 71 151 11 7 4 190 43 147 12 9 MN 2009-2013 11 55 All 222 61 161 11 3 8 197 44 153 5 9 Night 50 13 37 6 1 5 40 8 32 0 4 All states 20092013 76 380 All 2,850 853 1,997 102 29 73 2,571 647 1,924 89 88 Night 682 223 459 39 16 23 596 160 436 27 20
From page 143...
... 143 Table 60. Crash counts by collision type and manner of collision and crash severity at urban, five-leg signalized intersections Collision Type Total FI PDO Single-Vehicle Crashes Collision with parked vehicle 4 0 4 Collision with animal 0 0 0 Collision with fixed object 24 9 15 Collision with other object 2 0 2 Other SV collision 70 18 52 Noncollision 2 2 0 All SV crashesa 102 29 73 Multiple-Vehicle Crashes Rear-end collision 1,104 275 829 Head-on collision 88 42 46 Angle collision 665 208 457 Sideswipe collision 357 32 325 Other multiple-vehicle collisions 357 90 267 Total MV crashesa 2,571 647 1,924 Total Crashesa 2,673 676 1,997 a Note crash counts do not include pedestrian and bicycle crashes 6.3 Safety Performance Functions -- Model Development Intersection SPFs were developed in the forms illustrated by Equations 50 through 52: 𝑁 = 𝑒π‘₯𝑝 π‘Ž + 𝑏 Γ— ln 𝐴𝐴𝐷𝑇 + 𝑐 Γ— ln(𝐴𝐴𝐷𝑇 )
From page 145...
... 145 All of the vehicle-pedestrian and vehicle-bicycle crashes predicted with Equations 9 and 12 are assumed to be FI crashes (none as PDO)
From page 146...
... 146 Table 61. SPF coefficients for five-leg intersections with signal control on urban and suburban arterials-MV crashes (AADTs separate for major-, minor-, and fifth-roads)
From page 147...
... 147 Table 64. SPF coefficients for five-leg intersections with signal control on urban and suburban arterials-SV crashes (AADTs separate for major-, minor-, and fifth-roads)
From page 148...
... 148 Figure 49. Graphical representation of the SPF for MV total crashes at five-leg intersections with signal control on urban and suburban arterials (based on model for MV total crashes in Table 61)
From page 149...
... 149 Figure 51. Graphical representation of the SPF for MV PDO crashes at five-leg intersections with signal control on urban and suburban arterials (based on model for MV PDO crashes in Table 61)
From page 150...
... 150 Figure 53. Graphical representation of the SPF for SV FI crashes at five-leg intersections with signal control on urban and suburban arterials (based on model for SV FI crashes in Table 66)
From page 151...
... 151 and bicycle crashes, respectively, for five-leg intersections with signal control on urban and suburban arterials. Table 67.
From page 152...
... 152 Table 68. Distribution of SV crashes for five-leg intersections with signal control on urban and suburban arterials Manner of Collision Percentage of SV Crashes Five-Leg Signalized Intersections (5SG)
From page 153...
... 153 vehicles traveling through five-leg intersections due to the need for more signal phases. Then, as the minor- and fifth-road volumes increase, the predicted crashes for five-leg signalized intersections exceed the predicted crashes for four-leg signalized intersections.
From page 154...
... 154 β€’ CMFs developed as part of this research based on a cross-sectional study design and regression modeling; β€’ CMFs already incorporated into the first edition of the HSM and applicable to urban fiveleg signalized intersections; and β€’ High-quality CMFs applicable to urban five-leg signalized intersections developed using defensible study designs (e.g., observational before-after evaluation studies using SPFs – the EB method) , as referenced in FHWA's CMF Clearinghouse with four or five-star quality ratings or based on a review of relevant intersection safety literature.
From page 155...
... 155 The final models recommended for inclusion in the second edition of the HSM include: β€’ The model for MV total crashes in Table 61 β€’ The model for MV FI crashes in Table 62 β€’ The model for MV PDO crashes inTable 61 β€’ The model for SV total crashes in Table 66 β€’ The model for SV FI crashes in Table 66 β€’ The model for SV PDO crashes in Table 66 Attempts to develop SDFs for five-leg intersections with signal control on urban and suburban arterials proved unsuccessful for the reasons explained in Section 4.6. Therefore, it is recommended for the second edition of the HSM that crash severity for five-leg intersections be addressed in a manner consistent with existing methods in Chapter 12 of the HSM, without use of SDFs.

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