Intersection Crash Prediction Methods for the Highway Safety Manual (2021) / Chapter Skim
Currently Skimming:
Pages 79-98
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 79... ...
79 Chapter 4. Development of Models for Use in HSM Crash Prediction Methods: Three-Leg Intersections with Signal Control on Rural Highways This section of the report describes the development of crash prediction models for three-leg intersections with signal control on rural highways and presents the final models recommended for incorporation in the second edition of the HSM.
|
From page 80... ...
80 • The traffic control at the intersection was something other than signal control. • The number of intersection legs was not three.
|
From page 81... ...
81 Table 17. Site characteristic variables collected for three-leg intersections with signal control on rural highways (Continued)
|
From page 82... ...
82 4.2 Descriptive Statistics of Database A total of 161 sites -- 89 on two-lane and 72 on multilane highways -- were available for development of crash prediction models. The data collections sites were located in eight states: California, Florida, Illinois, Kentucky, Michigan, New Hampshire, Ohio, and Washington.
|
From page 83... ...
83 Table 19. Major- and minor road AADT statistics by roadway classification for rural three-leg intersections with signal control State Date Range Number of Sites Number of Site-Years Major Road AADT (veh/day)
|
From page 84... ...
84 Table 21. Crash counts by collision type and manner of collision and crash severity at three-leg intersections with signal control on rural two-lane highways Collision Type Totala FI PDO SINGLE-VEHICLE CRASHES Collision with animal 16 0 16 Collision with bicycle 3 2 1 Collision with pedestrian 0 0 0 Overturned 16 13 3 Ran off road 1 0 1 Other SV crash 137 35 90 Total SV crashes 173 50 111 MULTIPLE-VEHICLE CRASHES Angle collision 171 74 75 Head-on collision 24 16 8 Rear-end collision 408 120 220 Sideswipe collision 43 7 22 Other MV collision 68 15 39 Total MV crashes 714 232 364 Total Crashes 887 282 475 a Crash records did not indicate severity level for a number of crashes for some intersections in Florida and Kentucky; FI and PDO crashes will not add up to total crashes in some cases.
|
From page 85... ...
85 Based on a review of the number of states, sites, site-years, and crashes for the database assembled, data for all sites were used for model development to maximize the sample size rather than using a portion of the data for model development and a portion for model validation. All SPFs were developed using a NB regression model based on all sites combined within a given area type and intersection type.
|
From page 86... ...
86 • Installation of left-turn lanes: use CMF2i shown in Table 30 (same as Tables 10-13 and 11-22 in the HSM with the addition of a CMF for three-leg intersections with signal control) • Installation of right-turn lanes: use CMF3i shown in Table 31 (same as Tables 10-14 and 11-23 in the HSM with the addition of a CMF for three-leg intersections with signal control)
|
From page 87... ...
87 Figure 13. Graphical representation of the SPF for total crashes at three-leg intersections with signal control on rural two-lane highways Figure 14.
|
From page 88... ...
88 Figure 15. Graphical representation of the SPF for PDO crashes at three-leg intersections with signal control on rural two-lane highways The final SPF models for crashes at three-leg intersections with signal control on rural multilane highways are shown in Table 25, separately for each crash severity.
|
From page 89... ...
89 Figure 16. Graphical representation of the SPF for total crashes at three-leg intersections with signal control on rural multilane highways Figure 17.
|
From page 90... ...
90 Figure 18. Graphical representation of the SPF for PDO crashes at three-leg intersections with signal control on rural multilane highways Similar to Tables 10-5 and 10-6 in the HSM, respectively, Tables 26 and 27 provide percentages for crash severity levels and collision types and manner of collision, respectively, for three-leg intersections with signal control on rural two-lane highways.
|
From page 91... ...
91 Table 27. Distributions for collision type and manner of collision and crash severity at three-leg intersections with signal control on rural two-lane highways Collision Type Percentage of Total Crashes Total FI PDO SINGLE-VEHICLE CRASHES Collision with animal 1.8 0.0 3.4 Collision with bicycle 0.3 0.7 0.2 Collision with pedestrian 0.0 0.0 0.0 Overturned 1.8 4.6 0.6 Ran off road 0.1 0.0 0.2 Other SV crash 15.4 12.4 18.9 Total SV crashes 19.4 17.7 23.3 MULTIPLE-VEHICLE CRASHES Angle collision 19.3 26.2 15.8 Head-on collision 2.7 5.7 1.7 Rear-end collision 46.0 42.6 46.3 Sideswipe collision 4.8 2.5 4.6 Other MV collision 7.7 5.3 8.2 Total MV crashes 80.5 82.3 76.6 Total Crashes 100.0 100.0 100.0 Similar to Table 11-9 in the HSM, Table 28 provides percentages to break down total, FI (both with and without level C injuries)
|
From page 92... ...
92 Figure 19 illustrates a comparison of the predicted average crash frequency for total crashes based on the 3SG model for rural two-lane roads (Table 24) to the predicted average crash frequency based on the 3SG model in Chapter 12 of the HSM.
|
From page 93... ...
93 Figure 20. Comparison of new crash prediction model to existing model in HSM: 3SG for rural multilane highways vs 3SG for urban and suburban arterials (total crashes)
|
From page 94... ...
94 • The CMF for intersection lighting based on the work by Elvik and Vaa (2004) , which is identified for use with the intersection crash prediction models in Chapters 10 and 11 of the first edition of the HSM • The CMFs for providing a left-turn lane on one or two intersection approaches at a rural three-leg signalized intersection based on the work by Harwood et al.
|
From page 95... ...
95 decision to remove or change the lighting CMFs is made, this should be done consistently for all facility types as part of the development of the HSM second edition. Intersection Approaches with Left-Turn Lanes CMF With the CMF for providing a left-turn lane on one or two intersection approaches at a rural three-leg signalized intersection based on the work by Harwood et al.
|
From page 96... ...
96 4.5 Severity Distribution Functions The development of SDFs was explored for three-leg intersections with signal control on rural two-lane and multilane highways using methods outlined in Section 2.2.3 of this report. SDFs were not used in the development of crash prediction methods in the first edition of the HSM but were subsequently used in the Supplement to the HSM for freeways and ramps (AASHTO, 2014)
|
From page 97... ...
97 PK|KAB,3SG,at = probability of a fatal crash given that the crash has a severity of either fatal, incapacitating injury, or non-incapacitating injury for three-leg signalized intersections (3SG) based on all collision types (at)
|
From page 98... ...
98 The final predictive model for estimating total crashes at three-leg intersections with signal control on rural two-lane highways presented in Table 24 and the final predictive models for estimating total and FI crashes at three-leg intersections with signal control on multilane highways presented in Table 25 are recommended for inclusion in the second edition of the HSM, consistent with existing methods in HSM Chapters 10 and 11. Logical interpretations do exist for the SDFs reported in Section 4.5.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.