In-Service Performance Evaluation of Concrete Sloped End Treatments in Iowa
REPORT NUMBER
TRP-03-421-20
AUTHORS
Jessica Lingenfelter, Cody Stolle, Bob Bielenberg, Kyle Clute
PUBLICATION DATE
2020-10-12
ABSTRACT
Sloped end treatments were historically developed as low-cost, low-maintenance end treatments for rigid features like concrete barriers and bridge rails. Crash testing indicated that sloped end treatments are associated with significant instability and rollover risk for impacting vehicles. However, the in-service performance of these features has not been evaluated. An in-service performance evaluation (ISPE) was performed to evaluate vehicle crashes with sloped end treatments in Iowa between 2008 and 2017. Researchers generated a geographic inventory of sloped end treatment locations, reviewed crash narratives and scene diagrams for crashes near these sloped end treatments, and calculated an estimated crash rate and crash cost for these sloped end treatments. A total of 30 crashes were identified which involved sloped end treatments, including one fatal crash and one severe injury crash. Thirteen of the 30 crashes resulted in vehicle rollover (43%), and the estimated crash cost for sloped end treatments was approximately $178,260 per crash. For comparison, crash costs for other fixed objects in the same vicinity as sloped end treatments, typically associated with roads with higher speed limits, averaged $67,449 per crash. Benefit-cost analyses were calculated for replacing select groups of sloped end treatments with various crash cushions. Because nineteen of the crashes occurred on a total of seven bridges, indicating most impacts were in “black spot” locations, researchers recommended a sloped end treatment removal and replacement prioritization based on crash history. Further research is necessary to determine if Iowa crash results are extrapolatable to other states, as well as what safety treatments are preferred in challenging locations such as limited right-of-way or adjacent to intersections.
KEYWORDS
In-Service Performance Evaluation, End Treatment, Concrete Barriers, MASH, Injury Analysis, Benefit-to-Cost Ratio