NCHRP 22-13(2) [Completed]
Expansion and Analysis of In-Service Barrier Performance Data and Planning for Establishment of a Database
| Project Data
|Worcester Polytechnic Institute
|Malcolm H. Ray
Background: Significant improvements in roadside safety have been achieved through a multitude of action over the past three decades. However, roadside crash data indicate that over 40% of highway fatalities involve vehicles hitting objects on the roadside. Highway designers have developed several generations of traffic barriers to address these roadside safety problems, but there is not a full understanding of the effectiveness of traffic barriers in the field. While the crashworthiness criteria have been established in NCHRP Report 350 "Recommended Procedures for the Safety Performance Evaluation of Highway Features," the tests are based on idealized installations of barriers. In field installations the barrier may be located on sloped terrain, struck at different angles, subjected to the effects of settlement, installed improperly, and maintained less often than prescribed. These and other factors can influence the in-service performance of the barrier, but there has only been limited effort to investigate their effects. Transportation agencies (federal, state, and local) need guidance on the in-service performance of traffic barriers to make effective decisions on their use under specific conditions.
The American Association of State Highway and Transportation Officials' (AASHTO) Roadside Design Guide (RDG) provides general guidelines to assist design personnel in determining when specific highway-safety features may be needed. The RDG presents these guidelines in terms of roadside terrain, traffic volumes, design speed, accident probability, and environmental conditions. This guidance is, however, based upon limited in-service performance data and only general reference to applicability under specific conditions. In-service performance evaluations of roadside barriers are needed to (1) obtain the data necessary to fully understand performance, (2) determine the appropriate applications of barriers under specific conditions, (3) develop warrants, (4) improve installation and maintenance practices, (5) modify barrier and highway design standards where necessary, and (6) develop more realistic crash test criteria.
NCHRP Project 22-13 "In-Service Performance of Traffic Barriers" has made significant progress toward (1) developing practical procedures for gathering in-service performance data, (2) establishing a database for the in-service performance evaluations, and (3) sharing the information and insights gained. The current project is limited, however, to gathering in-service performance data for a subset (four types) of all barriers. The need exists to establish a comprehensive database for all commonly used barriers and typical field applications. This continuation will focus on extending (without interruption) the data gathering efforts to cover additional types of barriers in other regions. From the data gathered in these investigations, improved guidelines for a wider variety of barrier applications can be developed which consider the critical performance aspects of barriers (e.g., impact failure modes, life-cycle costs, durability, and maintainability). Such guidelines will aid in the selection of appropriate traffic barriers for a particular site.
Objective: The objectives of this research were to (1) extend the in-service performance evaluation database, (2) develop insights on hardware effectiveness from analysis of the data gathered, and (3) establish means to access, maintain, supplement, and disseminate data on in-service performance. It is intended that data collected in this continuation effort will be compatible with data already collected and that various analyses will be updated when significant increases in the available data occur. It is expected that a national repository will be established that will allow convenient access to the data.
Tasks: To accomplish the above objectives, the following tasks were performed: (1) Assess the procedures used in the first phase of this research for gathering in-service performance data. Determine opportunities for streamlining the process, making more efficient use of team members, and/or processing the data. Indicate the modifications that may be necessary to gather data for other commonly used types of hardware to facilitate efforts by the states. Review the potential for expanding the number and detail of data elements, such as estimating vehicle speeds prior to impact. (2) Continue gathering data using the modified procedures for the devices and locations approved by the panel. The proposer is expected to indicate the locations that would be used and any changes in the criteria for selecting crashes. (3) Identify at least four agencies willing to implement the in-service performance evaluation for a minimum of a one-year period. Provide on-site training for staff from these agencies and assist in the modification of the procedures to capture in-service performance data for the types of devices important to them. Initiate appropriate quality reviews to ensure data integrity and train agency personnel relative to means to maintain data quality. Coordinate efforts to add the data generated by the agencies into the existing database. (4) Establish a repository for all data gathered and conduct appropriate quality control checks. Provide quarterly summaries of the data in the repository. Establish metadata requirements to document the sources, transformations, and other aspects of the data. (5) Conduct analyses of the data gathered in both phases of this research to demonstrate the usefulness of a large national, detailed in-service performance database. Update completed analyses when significant additions to the relevant data occur. Prepare a technical brief of these analyses suitable for publication as an NCHRP research results digest. (6) Develop a plan for a long-term, national repository of in-service performance data. Identify an appropriate home for this data and outline procedures for gathering, indexing, accessing, and processing the data. Outline the data management and dissemination functions that would be performed, including: maintaining a library of performance evaluation studies, providing notification of potential new safety problems based upon the data, establishing priorities for future data collections, and coordinating data collection efforts across the nation. (7) Prepare comprehensive guidelines for conducting in-service performance evaluations. These guidelines would provide the basis for future efforts in this area. (8) Prepare a final report which documents the entire research effort including the initial phase of the project.
Status: The draft final report and procedures manual has been published as NCHRP Report 490: In-Service Performance of Traffic Barriers. Download Complete Report (1.8MB), not including Appendix D (6.1MB).
Product Availability: The contractor's draft final report for the first phase of this research, NCHRP Project 22-13, is available for loan. This report and a draft version of the procedures manual are available on the project website at https://www.WPI.EDU/Academics/Depts/CEE/Roadsafe/ISPE/.