The National Academies

NCHRP 22-23 [Completed]

Criteria for Restoration of Longitudinal Barriers

  Project Data
Funds: $300,000
Research Agency: Virginia Tech
Principal Investigator: H. Clay Gabler
Effective Date: 6/1/2006
Completion Date: 11/30/2009


Transportation agencies expend resources to ensure that all longitudinal barriers meet the safety performance guidelines to which they were constructed. Barrier systems are damaged by a wide variety of activities and factors, including minor crashes, snow plowing, mowing operations, and deterioration due to environmental conditions. Such damage may or may not be repaired by maintenance forces. For example, snowplows often bend W-beam guardrails and sometimes bend or break the posts. Even seemingly insignificant barrier damage or deterioration may compromise a barrier's safety performance.

With limited maintenance budgets, state highway agencies often have large backlogs of needed safety-feature repairs. These agencies cannot afford to repair damage that does not alter a barrier's safety performance, but significant barrier damage must be repaired to provide adequate protection for the motoring public. Unfortunately, in the absence of objective criteria for determining when repair is not required, highway agencies may be held to the unachievable standard of maintaining all safety features in as-built condition to avoid tort liability. Therefore, there is a need for objective, quantitative criteria in the form of guidelines for assessing damage and deterioration and determining when a longitudinal barrier requires repair or can remain in service.


The objective of this project is to develop guidelines to assist maintenance personnel in identifying the levels of damage and deterioration to longitudinal barriers that require repairs to restore operational performance.

The guidelines will assist the user in identifying longitudinal barriers and their components that require replacement or repair. Quantitative-based guidelines should be developed for semi-rigid and flexible barrier systems. The project should focus on longitudinal barriers within the length-of-need. It is expected that the study may include mathematical analysis, simulation, or full-scale crash testing to develop a correlation between the various levels of damage and deterioration and the degree of operational degradation to different types of barrier systems. Interactions between various types of damage and deterioration should also be considered. Key analysis findings developed under this project need to be validated.

Accomplishment of the project objective(s) will require at least the following tasks.

TASKS (1.) Identify and review completed and ongoing research and activities, including international sources, related to the project objective. (2.) Conduct a survey of state and Canadian provincial transportation agencies to gather existing policies and guidelines governing inspection and repair of longitudinal barriers. The survey should be used to identify the barrier systems and the types of damage and deterioration that should be considered in this project. (3.) Submit an interim report that, as a minimum, includes the following:
  • The results of Tasks 1 and 2 with a discussion of the critical findings.
  • A discussion of the objective criteria, to be developed, for quantifying damage and deterioration related to barrier performance.
  • An updated, detailed work plan, including the research approach and costs to evaluate each damage and deterioration type identified in Task 2.
  • A preliminary draft outline of the proposed guidelines.

(4.) Meet in Washington, D.C. with the NCHRP panel to review the Task 3 interim report approximately 1 month after its submittal. After the meeting, submit a revised interim report addressing the review comments and decisions at the meeting. (5.) Execute the approved work plan. (6.) Submit the preliminary draft guidelines for review by the panel. Revise the guidelines addressing the review comments. (7.) Submit a final report documenting the entire research effort. The final report shall describe how the project was conducted and include an appendix with the guidelines.

Status: The project has been completed and the revised final report published.

Product Availability: NCHRP Report 656, "Criteria for Restoration of Longitudinal Barriers"

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