Methodology to Predict the Safety Performance of Urban and Suburban Arterials (2008) / Chapter Skim
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Pages 66-87
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From page 66... ...
63 CHAPTER 4. DEVELOPMENT OF PROJECT DATABASE This section of the report describes the project database that was analyzed in the development of the HSM methodology for urban and suburban arterials.
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64 In Minnesota, urban and suburban arterial roadway segments of these types were selected on state routes under the jurisdiction of the Minnesota Department of Transportation and on county roads in Hennepin and Ramsey Counties. Most of the state highway routes and all of the county roads that were studied were located in the Twin Cities metropolitan area.
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65 TABLE 13. Summary of total length of study sites for arterial roadway segments Length of study sites (mi)
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66 DATA COLLECTION Several types of data were collected for each study site including site characteristics and accident data. The collection of each of these types of data for both roadway segments and intersections is addressed below.
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67 TABLE 15. Site characteristics data obtained for roadway segments on urban and suburban arterials Data element Description of data element Primary source Beginning landmark Name of intersecting street or other landmark at beginning of block Highway agency data or field review Beginning milepost Milepost or log mileage at beginning of block to tie field locations to accident data Highway agency data Bicycle route (marked)
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TABLE 15. Site characteristics data obtained for roadway segments on urban and suburban arterials (Continued)
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69 Roadside hazards are rated on a 1 to 7 scale developed by Zegeer et al (9) with 1 representing the best-designed roadside and 7 representing a poorly-designed roadside.
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70 TABLE 16. Site characteristics data obtained for intersections on urban and suburban arterials Data element Description of data element Primary source Data for Intersection as a Whole Angle of intersection Angle between intersecting streets (90° for right-angle intersections; less than 90° for skewed intersections)
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TABLE 16. Site characteristics data obtained for intersections on urban and suburban arterials (Continued)
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TABLE 16. Site characteristics data obtained for intersections on urban and suburban arterials (Continued)
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TABLE 16. Site characteristics data obtained for intersections on urban and suburban arterials (Continued)
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74 • Accidents on an intersection leg within 76 m (250 ft) of the intersection were assigned to the intersection if they were classified by the investigating office or accident coder as "intersection related"; otherwise, they were assigned to the roadway segment that contains the intersection leg.
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75 not be attributed to either the intersection or a roadway segment. Where two intersections are less than 152 m (500 ft)
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76 Table 19 summarizes the number of roadway segment sites (blocks) and their total length, average traffic volume, total exposure (million veh-mi of travel)
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77 TABLE 20. Roadway segment accident distribution by roadway type and jurisdiction Number (percentage)
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78 TABLE 23. Summary of intersection accident and exposure data Intersection type Number of intersections Average major-road ADT (veh/day)
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79 TABLE 25. Distribution of manner of collision for multiple-vehicle intersection collisions in Minnesota and North Carolina combined Percentage of accidents for each intersection type Collision type 3ST 3SG 4ST 4SG Rear-end 48.5 51.7 42.5 50.7 Head-on 0.5 0.6 0.9 0.7 Angle 38.1 33.0 44.8 34.4 Sideswipe, same direction 7.7 10.2 6.1 9.2 Sideswipe, opposite direction 0.4 0.4 0.8 0.4 Other multiple-vehicle collisions 4.8 4.1 4.9 4.7 TABLE 26.
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80 TABLE 27. Variables considered in safety prediction modeling Variable Multiple-vehicle nondriveway collisions Single-vehicle collisions Driveway-related accidents Roadway Segments Traffic volume (ADT)
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81 TABLE 28. Descriptive statistics for continuous variables for roadway segments Minnesota Michigan Variable/statistic 2U 3T 4U 4D 5T 2U 3T 4U 4D 5T ADT (veh/day)
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82 TABLE 29. Percentage of roadway segments in specific categories by state and roadway type Minnesota Michigan Variable/category 2U 3T 4U 4D 5T 2U 3T 4U 4D 5T On-street parking None 73 79 65 90 97 95 97 91 100 99 One Side < 1 9 6 3 < 1 2 3 5 1 Both Sides 27 12 29 7 2 4 4 Speed category Low (30 mph or less)
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83 TABLE 31. Percentage of intersections in specific categories by state and intersection type Minnesota North Carolina 3ST 3SG 4ST 4SG 3ST 3SG 4ST 4SG Speed category Low (30 mph or less)
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