Kimley > Horn
The analysis was conducted on the roadway network that consists of all City facilities and also TxDOT arterials . TxDOT highways , interstates , and frontage roads were not included in the analysis . City facilities correspond to all roadways that are maintained by the City of Arlington within their city limits . All vehicular unit KAB crashes totaled 4,004 on the analyzed roadway network . There are 313 bicycle and pedestrian KAB crashes on City facilities and TxDOT arterials , all of which involved a vehicle and are accounted for in the total 4,004 KAB crashes .
ANALYSIS METHODS
The following sections use the phrase roadway “ segment ” to describe small sections of the roadway network , typically starting and ending at street intersections .
Total Number of Crashes The calculation of the total number of KAB crashes along the network is from a GIS spatial analysis tool to sum the total number of KAB crashes that are within a distance to each roadway segment in the network . A spatial join with a buffer of 75 feet collected and counted each KA crash adjacent to each roadway segment .
Crashes are often located at or near intersecting roadway segments and multiple segments will count a single crash event within the 75 ft buffer . The influence area of the crash often covers multiple segments , depending on where segments are broken up . This occurrence is handled in the screening process of the high-injury network where high crash segments are joined together .
Using TxDOT ’ s HSIP guidance , the cost per crash for KA crashes is 12 times that of B crashes . KA crashes were weighted with a factor of 12 in calculating the total number of crashes at each roadway segment . This allows for a higher selection of fatal and severe injury crash segments while also including segments with many minor crashes .
Crash Frequency Crash frequency is the number of crashes per mile of roadway . It is calculated with the number of KAB crashes at each segment divided by the length in miles of the segment .
Critical Crash Rate The critical crash rate considers daily volumes , functional class , and crash count for each road segment . The road segment critical crash rate is calculated in the following steps :
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• HMVMT = 100,000,000 vehicle-miles travelled
• Vol = AADT or daily volume ( Replica Data – Spring 2023 )
• n = Number of years of crash history data
• mi = Length of segment in miles
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APPENDIX A : HIGH INJURY NETWORK METHODOLOGY A-3