NCHRP 22-12 [Completed]
Guidelines for the Selection, Installation, and Maintenance of Highway-Safety Features
| Project Data
|Texas A&M University
|C. E. Buth and Dean L. Sicking
Background: Recent research has promoted the concept of matching highway-safety features to the type of roadway facility and its traffic conditions. According to NCHRP Report 350, "Recommended Procedures for the Safety Evaluation of Highway-Safety Features," a safety feature may be developed to meet one of up to six test levels, depending on the type of feature. Further, a feature may be designed for temporary (work zone) or permanent applications. Under this concept, features developed for the lower test levels, which have minimal containment capabilities for heavier vehicles, may be considered applicable for low-speed, low-volume conditions. While the test levels have been defined, recommended guidelines for their application have only been developed for bridge rails. Transportation agencies (federal, state, and local) are being required to make decisions on the use of features to comply with NCHRP Report 350 without guidelines on the appropriateness of highway-safety features including permanent and temporary traffic barriers, crash cushions, terminals, truck-mounted attenuators, breakaway supports, rumble strips, and cross-sectional elements for 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 features, traffic volumes, design speed, accident probability, and environmental conditions. It does not, however, provide guidance on the specific type of highway-safety feature most appropriate for combinations of these conditions. Objective guidelines are needed not only to identify site conditions where a safety feature is needed but also to identify the most appropriate feature for that site. The guidelines should take into account roadway and traffic conditions, and the characteristics of candidate features (e.g., impact performance, life-cycle costs, durability, and maintainability). Inappropriate selection of a highway-safety feature at a particular site can be detrimental to the overall safety of the roadway or wasteful of scarce resources.
Improper installation of certain highway-safety features is known to contribute to the severity of accidents. Typically, it would be expected that hardware would be installed in accordance with manufacturer's instructions, but a considerable array of nonproprietary standard hardware exists for which there is little, if any, installation instruction. Even for proprietary hardware, instructions may not be available in the field at the time of installation or may not be written in a manner that is easily understood by installation personnel. Proper maintenance of highway-safety features is necessary for them to perform properly, but often maintenance is not a high priority. Routine maintenance procedures need to be fully outlined for agency personnel. Further, when maintenance is required after an accident where a feature has been hit and is damaged, there is a need for a defined procedure regarding the action to be taken. While there is often a general policy to replace in-kind (even though the feature may be substandard), other possible courses of action include removal of the feature, repair, replacement with upgraded or improved device, or implementation of some site-specific treatment. Thus, there is a need for the development of a user-oriented manual that will (a) compile information on installation and maintenance procedures, (b) provide general guidance on good installation and maintenance practices, (c) offer objective guidance for systemwide upgrading of existing features, and (d) assist in justifying design deviations or field modifications. The manual should provide uniform coverage of existing devices and allow new devices to be added over time.
Objective: The objective of this research is to develop improved guidance for the selection, installation, and maintenance of highway-safety features based on the performance concept. Specifically, the research will address (a) selecting the appropriate highway-safety feature given the characteristics of a site, (b) installing highway-safety features, (c) maintaining highway-safety features to ensure effectiveness over time, and (d) upgrading existing highway-safety features and justifying design deviations or field modifications. The research should be applicable to all types of urban, suburban, and rural highways. This research effort will concentrate on nonproprietary features, but also compile information to be provided by manufacturers of proprietary hardware.
Tasks: To accomplish the project objectives, the following tasks are envisioned: (1) Perform a literature search to identify relevant research and contact transportation agencies to establish the current state of the practice. Synthesize the findings of relevant research and current practices in the user community for highway-safety feature selection, installation, and maintenance. From the synthesis, identify the critical factors that need to be considered, the roadside safety problems and situations in need of attention, and the usage of various highway-safety features. (2) Establish an advisory group of 10 experts approved by the NCHRP panel. This group is intended to provide insights from other perspectives (e.g., construction, maintenance, manufacturing), aid in the review of documents produced in this project, and participate in meetings with the project panel. (3) Outline a general process for the selection of highway-safety features that includes a framework for specific guidelines based on the test levels defined in NCHRP Report 350. Determine an effective approach (e.g., cost-effectiveness-based procedure) for establishing the specific criteria for selecting highway-safety features and describe how the guidelines will be developed and validated. The guidelines should provide objective selection criteria for new installations and guidance on upgrading or retrofitting existing features. The guidelines should include considerations of likely impact conditions, performance range, costs, existing maintenance practices and strategies, and other factors. In this task, assess the adequacy and limitations of the data and the selection factors to be used in the guidelines. Suggest methods to present and package the guidelines to facilitate their use. (4) Prepare an interim report that describes the process to be used to develop the guidelines for the selection of highway-safety features. The interim report must include a recommended methodology for validating the guidelines that will be developed. (5) Revise the proposed process for developing selection guidelines based on the recommendations of the NCHRP panel. After approval of the revised process, develop draft guidelines for the selection of highway-safety features and describe supplemental materials that could be developed (in other research) to facilitate the process. Document the processes used to develop the guidelines to enable agencies to revise, adapt, or update the guidelines for conditions specific to their area. (6) Validate the guidelines using the methodology approved in the interim report. Report the findings of the validation effort and recommend any changes that would improve the usefulness of the guidelines. (7) Outline a user-oriented manual to provide guidance on the installation and maintenance of highway-safety features. This manual should be designed to provide generic guidance as well as specific guidance for making the upgrades necessary to eliminate or improve substandard highway-safety features. Prepare an outline for the manual and develop a convenient format for the contents, which will serve the needs of users ranging from highway designers to field personnel. Because the most relevant information on installation and maintenance is available from manufacturers, propose a process for gathering information in a prescribed format for the inclusion in the manual. Describe supplemental materials or user aids that may be developed to facilitate the use of this manual. (8) Prepare a second interim report that describes the proposed installation and maintenance manual and meet with the project panel and advisory group to discuss the content and form of the proposed manual. (9) After NCHRP approval of the revised outline, prepare the manual in accordance with the revised outline. Develop generic guidance for installation and maintenance practices and include procedures for interaction with designers when situations warrant. Compile pertinent installation and maintenance information for the various nonproprietary roadside hardware elements. Contact suppliers of proprietary hardware to request installation and maintenance information. Include in the manual the information that is received from suppliers in the required format. Recommend appropriate supplemental materials and user aids (e.g., videotapes, field notes, computer software) to facilitate the use of this manual considering the needs of the users and the changing nature of the information. (10) Distribute the draft selection guidelines and the installation and maintenance manual for review by a larger user community. Compile the feedback received and recommend changes to the guidelines and manual for consideration by the project panel and advisory group. Participate in a third interim meeting to review the recommendations and determine which changes will be made. After the meeting, revise the guidelines and the manual in accordance with the directives of the panel. (11) Prepare a final report that documents the entire research effort. The revised selection guidelines and installation and maintenance manual developed in this research shall be included as separate volumes.
Status: A new project, NCHRP Project 22-12(2), will be initiated to complete the research started but not completed under this project. There are expectations that the products developed under NCHRP Project 22-12(2) will permit DOTs to implement performance-based warrants for roadside safety features. A contract with the University of Nebraska is in development for Project 22-12(2).
Product Availability: No products are currently available.