NCHRP Report 350
, "Recommended Procedures for the Safety Performance Evaluation of Highway Features," incorporated significant changes and additions to procedures for safety performance evaluation, including criteria for multiple performance levels, guidelines for testing features not previously addressed, translation to metric units, and updates reflecting the changing character of the highway network and the vehicles using it. However, some of the recommendations in NCHRP Report 350
were based on limited crash-test experience and subsequent testing has found that some existing hardware, which is believed to be performing adequately in the field, has difficulty passing the new tests and evaluation criteria. This problem has raised questions about the relevance and adequacy of the procedures. It was developed in an attempt to improve roadside safety by establishing crashworthiness criteria that would reflect changes to the vehicle fleet and safety hardware technology. However, the relevance of these procedures to overall roadside safety is not fully understood.
Other reasons for considering updates to NCHRP Report 350
arise from the assumptions that underlie it, technological advances that have occurred, and changes to other specifications. For example, NCHRP Report 350
was developed on assumptions that occupants of errant vehicles are unbelted, vehicles should be contained and redirected, and the test should reflect worst-case-scenario conditions. It is also assumed that the vehicles are stable and tracking and that the potential for occupant injury can be calculated from the vehicle changes in velocity. Technological advances in the state of the art of finite element analysis for design and evaluation of hardware are rapidly advancing and may offer other means to evaluate roadside hardware. Changes in the specifications referenced in the report (e.g., SAE, ASTM) may also need updates.
The objectives of this research were to (1) evaluate the relevance and efficacy of procedures for the safety-performance evaluation of highway features and (2) assess the needs for updates to NCHRP Report 350 and recommend strategies for implementing them.
To accomplish these objectives, the following tasks were conducted: (1) Review pertinent documents to identify issues and developments in crash testing and safety features. Conduct a survey of safety professionals to identify the key issues that may necessitate an update of NCHRP Report 350.
(2) Develop a prototype methodology and establish criteria for determining relevance of the procedures for safety-performance evaluation. It will be important that the methodology for assessing the relevance addresses both needs for improving safety and the current and near-term vehicle, infrastructure, and technological realities. (3) Conduct a preliminary assessment of specific needs for updates in the testing and reporting procedures in NCHRP Report 350
. For example, this assessment could include a review of changes in fleet characteristics, roadside-safety hardware, seat-belt usage, occupant-protection systems, in-service performance insights, instrumentation capabilities, and other factors related to safety-performance evaluation. (4) Prepare an Interim Report that provides preliminary recommendations for strategies to update NCHRP Report 350
. Meet with the project panel after they have reviewed the interim report to (a) assess the findings, (b) determine the focus of the remaining tasks, and (c) initiate discussions on strategies for updating. (5) Investigate the relevance of safety- performance evaluation procedures using the methodologies and criteria identified in Task 2. (6) Continue the assessment of updating needs for the procedures safety-performance evaluation as directed by the panel at the interim meeting. The contractor will undertake those work plans selected by the panel including gathering new data, performing pilot tests on instruments, evaluating costs and benefits, comparing crash-test data, conducting crash tests, or undertaking other analyses to evaluate the importance of updates, formulate specific new procedures, establish acceptance criteria, or similar efforts that will serve as the basis for updating the procedures. (7) Develop strategies for the update of NCHRP Report 350
considering urgency, new research results, emerging trends, costs, time requirements, probabilities of success, and other factors. This task is also intended to outline the fundamental and empirical research that may be necessary to address the issues identified and a time frame for when it should be undertaken. While a full update of NCHRP Report 350
will be needed, it would be useful to determine if an interim update is necessary. The strategies need to outline the staging and priorities of efforts and assess the impacts of not implementing each change. The outline should reflect the impacts of changes in the driver population, accident experience, increased traffic, greater variations in traffic mix, higher speed limits, and other external factors. (8) Prepare Interim Report (No. 2) that highlights the issues and the recommendations to address them. This task will provide the materials that will be used in Task 9. (9) Coordinate a critical review of the recommended strategies with a large group of knowledgeable professionals. This review will be intended to determine if it is feasible to proceed with specific changes to the procedures, assess the urgency associated with them, and review the potential impacts on users of NCHRP Report 350
. The contractor will be expected to organize the review, gather feedback, and make recommendations for changes in the strategies. The panel will provide input on the changes that should be made to the final report. (10) Prepare a final report that documents the efforts undertaken in the project, research findings, recommended updates to the procedures, proposed implementation strategy, and needs for future research.
The project has been completed. NCHRP Project 22-14(2) will now be initiated to begin the process of updating NCHRP Report 350.
The contractor's draft final report was sent to all state DOTs and is available on a loan basis from the NCHRP.