Scale and Scope of Safety Assessment Methods in the Project Development Process
Long Description
The predicted number of total segment-related crashes at divided urban multi-lane arterials equals the sum of number of multiple-vehicle non-driveway collisions and the number of single vehicle related crashes and the number of multiple vehicle driveway-related collisions (HSM Equation 12-4, p 12-5):
Multiple-vehicle non-driveway collisions calculated as:
- Number of multiple-vehicle non-driveway collisions equals the exponent of a plus the product of b and the natural log of AADT plus the natural log of the length of segment. (HSM Equation 12-10, p. 12-18)
Total Crashes calculated as:
- Average total crash frequency for multiple-vehicle non-driveway collisions equals the exponent of -12.34 plus the product of 1.36 and the natural log of 28,000 plus the natural log of 1 equals 4.885. (HSM Table 12-10, p. 12-18 (for 4-lane divided (4D)))
N-prime value for fatal plus injury crashes calculated as:
- The N-prime value for fatal and injury crashes for multiple-vehicle non-driveway collisions equals the exponent of -12.76 plus the product of 1.28 and the natural log of 28,000 plus the natural log of 1 equals 1.415. (HSM Table 12-10, p. 12-18 (for 4-lane divided (4D)))
N-prime value for property damage only crashes calculated as:
- The N-prime value for property damage only crashes for multiple-vehicle non-driveway collisions equals the exponent of -12.81 plus the product of 1.38 and the natural log of 28,000 plus the natural log of 1 equals 3.747. (HSM Table 12-10, p. 12-18 (for 4-lane divided (4D)))
Fatal plus injury crashes calculated as:
- Average fatal and injury crash frequency for multiple-vehicle non-driveway collisions equals the product of the average total crash frequency for multiple-vehicle non-driveway collisions and the N-prime value for fatal and injury crashes for multiple-vehicle non-driveway collisions divided by the sum of N-prime value for fatal and injury crashes for multiple-vehicle non-driveway collisions and the N-prime value for property damage only crashes for multiple-vehicle non-driveway collisions. (HSM Equation 12-11, p12-20)
Property damage only crashes calculated as:
- Average property damage only crash frequency for multiple-vehicle non-driveway collisions equals the difference between the average total crash frequency for multiple-vehicle non-driveway collisions and the average fatal and injury crash frequency for multiple-vehicle non-driveway collisions. (HSM Equation 12-12, p12-20)
- Average fatal and injury crash frequency for multiple-vehicle non-driveway collisions equals the product of 4.885 and 1.415 divided by the sum of 1.415 and 3.747 equals 1.339.
- Average property damage only crash frequency for multiple-vehicle non-driveway collisions equals the difference between 4.885 and 1.339 equals 3.547.
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