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1 CHAPTER 1 Introduction Longitudinal barriers, such as guardrails, are installed along 1.1 Research Problem Statement a roadway or in the roadway median to prevent an errant vehi- cle from traversing a steep slope, impacting a more danger- The research problem statement for the project is quoted ous roadside object, or entering opposing vehicle travel lanes. below: Full scale crash testing is used to evaluate the performance of these barriers prior to their installation along a highway (Ray Transportation agencies expend resources to ensure that all longitudinal barriers meet the safety performance guidelines to and McGinnis, 1997; Ross et al, 1993). Based on an evaluation which they were constructed. Barrier systems are damaged by a using real-world crash data, these barriers have consistently wide variety of activities and factors, including minor crashes, been shown to be effective (Short and Robertson, 1998; Michie snow plowing, mowing operations, and deterioration due to and Bronstad, 1994; Elvik, 1995). Very little is known, how- environmental conditions. Such damage may or may not be ever, with respect to how these barriers perform after they repaired by maintenance forces. For example, snowplows often have been damaged. bend W-beam guardrails and sometimes bend or break the posts. Even seemingly insignificant barrier damage or deterioration Highway agencies expend considerable resources to repair may compromise a barrier's safety performance. damaged longitudinal barriers. Limited funds prevent high- With limited maintenance budgets, state highway agencies way agencies from maintaining all field-installed systems in often have large backlogs of needed safety-feature repairs. These an ideal as-built condition. Instead, these agencies focus on agencies cannot afford to repair damage that does not alter a bar- repairing only damage that is perceived to have a detrimental rier's safety performance, but significant barrier damage must be effect on the safety performance of the barrier. The distinc- repaired to provide adequate protection for the motoring public. Unfortunately, in the absence of objective criteria for determin- tion between minor damage and more severe performance- ing when a repair is not required, highway agencies may be held altering damage, however, is not always clear. In the case of to the unachievable standard of maintaining all safety features in a high severity crash involving rail penetration (left image in as-built condition to avoid tort liability. Therefore, there is a need Figure 1), the need for barrier repair is obvious. Much more for objective, quantitative criteria in the form of guidelines for common, though, is minor barrier damage, e.g., a shallow assessing damage and deterioration and determining when a dent which occurs in a low-speed collision or a sideswipe longitudinal barrier requires repair or can remain in service. (right image in Figure 1). Minor damage to barriers may also result from routine highway maintenance operations, includ- 1.2 Objectives and Scope ing snowplowing, mowing or paving, and exposure to the environment, which may result in corrosion or termite damage. The objective of this project was to develop guidelines to Regardless of the cause, damage of this type poses a challenge assist maintenance personnel in identifying the levels of dam- to highway agencies. A failure to repair damage that affects age and deterioration to longitudinal barriers that require barrier performance may lead to fatal consequences for pass- repairs to restore operational performance. The scope of this ing motorists as well as potential exposure of the agency to a project was limited to w-beam barriers, which are by far the tort liability claim. Crash testing of undamaged barriers has most common barrier in use in the United States. The primary consistently demonstrated that seemingly insignificant alter- focus was on the barrier length of need sections. Although spe- ations to a barrier, such as using a rectangular washer on the cific end terminals were not in the scope of this project, generic post-rail connection, may result in catastrophic consequences guidance applicable to all end terminals was included in the for an impacting vehicle. This underscores the importance of recommended guidelines but was not quantitatively evaluated. the ability of agencies to identify seemingly minor damage that It is also important to note what was not covered under has serious implications on crash performance. the scope of this project. The guidelines pertained only to the