NCHRP 22-08 [Completed]
Evaluation of Performance Level Selection Criteria for Bridge Railings
| Project Data
||Texas A&M University|
||King K. Mak |
The Guide Specifications for Bridge Railings (the Guide Spec) has been adopted by the American Association of State Highway and Transportation Officials (AASHTO). It incorporates a multiple performance-level concept, which tailors a bridge rail to the design speed, ADT, traffic mix, roadway design characteristics, and nature of the elements beneath the bridge at a site. The Guide Spec also requires that future bridge railings be crash tested to confirm that they meet the requirements of the specified performance level. The application of the performance-level approach will provide the opportunity to match bridge rail designs to the conditions at a site.
The objectives of this research were (1) to determine the adequacy and validity of the performance levels and the performance-level selection procedures contained in the Guide Spec, (2) to estimate the impact of implementing the Guide Spec on state and local agencies, (3) to recommend appropriate improvements to the Guide Spec, and (4) to evaluate the feasibility of extending the multiple performance-level approach to all longitudinal barrier systems. This research involved the following tasks: (1) Reviewed the literature for information on the multiple performance-level concept, barrier warrants, barrier design, vehicle crash testing, accident studies involving vehicle contact with bridge railings and other longitudinal barrier systems, and any other related subjects to validate the criteria used to develop the performance levels identified in the Guide Spec. (2) Evaluated the sensitivity of the performance-level criteria using simulation analysis and accident data. (3) Documented problems with the software used to develop the Guide Spec and made necessary modifications. Reproduced the barrier performance-level tables as necessary and reassessed the sensitivity after modifications to the software. (4) Compared the revised barrier performance selection tables with the existing Guide Spec and discussed the implications of differences in these tables on the design requirements. Data from typical bridges were obtained from states to indicate the implications. (5) Evaluated the feasibility of extending the multiple performance-level concept to all longitudinal barriers. (6) Prepared a series of white papers describing improvements to the analysis software and procedures as well as basic research needs deemed necessary to evaluate roadside safety. (7) Prepared metric versions of revised Guide Spec warrants.
Status: This project has been completed. The results addressed the concerns of the AASHTO Bridge Committee and served as the basis for efforts in NCHRP Project 22-9.