AASHTO released a supplement to the Highway Safety Manual (HSM) in 2014 that includes models for freeway interchanges composed of segments, speed-change lanes and terminals. A necessary component to the use of HSM is having the appropriate safety-related data. However, a high percentage, approximately 75 percent, of interchange crashes on the MoDOT TMS systems are landed on an incorrect location within an interchange. For example, crashes are frequently placed in the midpoint of the ramp terminal instead of properly assigned to one of the two ramp terminals. Another example is crashes that are assigned to the freeway mainline when the crashes are related to ramps. In order to properly calibrate and use HSM freeway interchange models, the location of crashes needs to be corrected. The crash landing correction involves the visual inspection of crash images compiled by the Missouri State Highway Patrol. A detailed procedure was established along with a reviewer test so that crash correction can be conducted uniformly among multiple reviewers. A total of 10,897 crashes were reviewed, and 9,168 underwent detailed review and correction. Of the total, 1482 were partial cloverleaf crashes, 5086 were diamond interchange crashes, 780 were ramp crashes, and 1820 were speed-change lane crashes. The crash location correction process helped to eliminate the error rate of 69% associated with interchange crash locations. Any analyst can correct crash locations by following the procedure detailed in this report. (Author/publisher)
Abstract