Kimley > Horn
• Ri = Observed crash rate
• Nobserved = Total number of crashes observed
3 . � � = ∑ ( ���∗� � ) ∑���
• Ra = Weighted average crash rate per functional class
4 . � � , � = � � + �� ∗ � � � �
� + �
����� ( �∗����� ) �
• Rc , I = Critical crash rate
• P = 1.645 , which corresponds to the 95 th % confidence level
5 . ����� = � �
� � , �
• If Ratio > 1 , observed crash rate is greater than critical crash rate so flag for potential high-injury network selection
SCORING
In order to score each method evenly and develop a balanced high-injury network ( HIN ), 20 % quantile ranges of the crash analysis data were used . Points were assigned to each quantile based off the total crash count , crash frequency , and critical crash rate ratios . The following outlines the points assigned to each :
• 1 point – 0 to 20 % Quantile
• 2 points – 20 to 40 % Quantile
• 3 points – 40 to 60 % Quantile
• 4 points – 60 to 80 % Quantile
• 5 points – 80 to 100 % Quantile
The following table summarizes the quantile ranges established for each method and each HIN :
Quantile Range
Total Number of Crashes ( Weighted )
Crash Frequency
Critical Crash Rate Ratio
Low High Low High Low High
Vehicular HIN 0 to 20 % 0 1 0 11.53 0 0.33 20 to 40 % 2 3 11.53 19.36 0.33 0.67 40 to 60 % 4 12 19.36 34.23 0.67 1.14
APPENDIX A : HIGH INJURY NETWORK METHODOLOGY A-4