Several guardrail end treatments have been used in Wisconsin in the past twenty years. The last statistical in-service safety performance evaluation of guardrail end treatments in Wisconsin was conducted by the Traffic Operations and Safety Lab (TOPS Lab) in 2008 and found that turn down guardrail ends provide the least effective safety record of all guardrail end treatments used in Wisconsin at that time. ET Plus is one of several crash test approved guardrail end treatments that has been used in Wisconsin. Recently, fifteen states, including Wisconsin, have taken ET Plus end treatment off their approved product lists following concerns about its safety performance due to a design change in 2005. American Association of State Highway and Transportation Officials’ (AASHTO) Manual for Assessing Safety Hardware (MASH) and the Federal Highway Administration (FHWA) encourage in-service performance evaluation of roadside safety hardware. The objective of this research is to statistically evaluate in-service safety performance of guardrail end treatments that are approved and available for installation in Wisconsin. Specifically, this research will compare ET Plus and SKT.