Mechanical & Materials Engineering, Department of


First Advisor

Cody Stolle

Date of this Version



Lingenfelter, J.L., In-Service Performance Evaluation of Concrete Sloped End Treatments in Iowa, Midwest Roadside Safety Facility, University of Nebraska-Lincoln, Lincoln, Nebraska, May, 2020.


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfilment of Requirements For the Degree of Master of Science, Major: Mechanical Engineering and Applied Mechanics, Under the Supervision of Professor Cody S. Stolle. Lincoln, Nebraska: May 2020

Copyright 2020 Jessica L. Lingenfelter


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 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, resulting in 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 was 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 prioritization of removal and replacement of sloped end treatments 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.

Advisor: Cody S. Stolle