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The National Academies

NCHRP 22-42 [Pending]

Impact Performance Assessment of Barrier Performance at High Speeds

  Project Data
Funds: $600,000
Contract Time: 36 months
Staff Responsibility: David M. Jared

BACKGROUND

The AASHTO Manual for Assessing Safety Hardware (MASH) specifies impact speeds for crash testing and evaluation of barrier systems such as guardrails, median barriers, and bridge rails. The highest impact speed defined by MASH for passenger vehicles is 62 mph. This impact speed was derived from analyses of reconstructed crash data that is nearly 20 years old.

Currently, 18 states have posted speed limits of 75 mph or higher. Seven of these states have posted speed limits of 80 mph, and one state has posted speed limits of 85 mph. With most of these states adopting such higher speeds within the past 5 years, there is a growing need for evaluating barriers at higher impact speeds to maintain appropriate barrier performance.

Increased impact speeds will place more demand on barrier systems. The performance limits of current barrier systems beyond the MASH design impact speed of 62 mph are not fully understood. Partial rail tears have been observed in guardrail systems tested under MASH impact conditions, indicating that these systems are near containment capacity. Research to assess performance limits of existing barrier systems for greater impact speeds is needed.

OBJECTIVES

The objectives of this research are the following:

1. Assess the performance of existing, non-proprietary longitudinal barriers on roadways with posted speeds of 75 mph and higher.

2. Identify needs for barrier test criteria at these higher speeds.

3. Develop, as needed, barrier test parameters that could be considered for future criteria and crash testing. At a minimum, these parameters shall include test vehicles, impact speed, angle of impact, and required impact results.

4. Develop cost-effective barrier design(s) to meet the developed test parameters and verify performance of the design(s).

This research shall evaluate existing, non-propriety barrier designs and exclude proprietary barrier, transition, and terminal designs.

Accomplishment of the project objectives will require at least the following tasks.

RESEARCH TASKS

Task descriptions are intended to provide a framework for conducting the research. The NCHRP is seeking the insights of proposers on how best to achieve the research objectives. Proposers are expected to describe research plans that can realistically be accomplished within the constraints of available funds and contract time. Proposals must present the proposers’ current thinking in sufficient detail to demonstrate their understanding of the issues and the soundness of their approach to meeting the research objectives.

Task 1. Review literature and state-of-practice on crashworthy longitudinal barrier systems on highways with posted speeds up to 85 mph. Conduct a safety analysis using barrier impact data on a range of highway speeds to determine how current high-speed barriers are performing relative to barriers with common posted speeds of 70 mph and below. If required, identify barrier conditions for particular posted speeds, vehicles, and barrier types that are underperforming.

Task 2. Develop preliminary barrier test parameters using findings from Task 1. Use finite element analysis (FEA) to refine these parameters as required.

Task 3. Submit a technical memorandum covering the findings of Tasks 1-2, prioritizing underperforming barriers for assessment, and including a plan for assessing the barrier conditions identified. This plan should outline what upcoming tasks can be achieved with remaining project funds and identify subsequent research that might be needed in the future. NCHRP approval of the technical memorandum and draft assessment plan must be obtained before work on remaining tasks begin.

Task 4. Simulate impact results for the higher speed barrier conditions identified in Tasks 1-3. Finalize proposed barrier test parameters. Identify failure mechanisms associated with any existing barrier designs as applicable. Identify existing barrier designs that may have the potential to meet higher speed impact conditions with only minor design modifications. Develop preliminary, cost-effective barrier designs to meet higher speed impact conditions identified in Tasks 1-3.

Task 5. Submit an interim report summarizing the findings from Tasks 1-4. Present findings to NCHRP at an interim meeting. NCHRP approval of the interim report is required before work on Task 6 may begin.

Task 6. Complete cost-effective barrier design(s) to meet higher speed impact conditions identified in Tasks 4-5. Verify performance of the barrier design(s) with crash simulations. Submit a technical memorandum summarizing the results of Task 6. NCHRP approval of the memorandum is required before work on Task 7 may begin.

Task 7. Conduct crash testing to verify crash simulations on barrier design(s) from Task 6. The research team shall arrange and oversee crash testing at a certified crash test facility that does not pose any conflicts of interest for the team.

Task 8. Submit a final report, covering Tasks 1-7, and associated deliverables.

Status: The contractor has been selected and contract execution is pending.

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