Each year, roadway departure crashes in the United States result in serious injuries and fatalities. Side impacts of vehicles into roadside hardware are a growing public safety problem. In particular, side impacts with guardrail account for a significant percentage of fatalities in passenger vehicle-guardrail crashes.
An occupant of a passenger vehicle that side impacts guardrail has a 30 percent higher probability of fatal injury than an occupant of a car that frontally impacts guardrail. Many roadside safety features, such as terminals, guardrail end treatments, crash cushions, and luminaire and sign supports, are designed to break away under typical loads for a frontal impact. However, side impacts by non-tracking vehicles may not have enough force to engage the breakaway mechanisms of these features. Because the side of a vehicle, unlike the front, has less structure and crumple zone, side impacts can result in especially severe injuries.
To date, however, no substantive improvements have been made to the performance of roadside safety features during vehicle side impacts. NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features provided information on side impacts through test and evaluation procedures thereon; however, it does not contain recommendations or requirements for side impact crash testing of roadside safety hardware (RSH). More recently, the NCHRP Report 350 appendix for side impact test and evaluation procedures was not included in the AASHTO Manual for Assessing Safety Hardware (MASH) crash test procedures. Little is known about how NCHRP Report 350- or MASH-compliant hardware performs in side impact crashes.
No research to date has developed a comprehensive approach for evaluating RSH under side impact conditions. The development of methods for evaluating these crashes would lead to improvements in RSH and improved safety for motorists. Results of this research could enable transportation agencies to establish levels of safety risk and use quantitative information to do so.
Under NCHRP Project 22-32, work began to develop this comprehensive approach and produced a report describing the following: (a) recommended test procedures for evaluating RSH under side impact conditions; (b) plan for validating two aspects of side impact performance: ability of side impact design improvements to lower occupant risk; and translation of lower occupant risk to fewer severe and fatal injuries in side impact crashes observed in the field; (c) preliminary recommendations for enhancements to MASH and RDG; and (d) work plan for side impact crash testing and finalizing side impact test procedures and evaluation criteria, with optional side impact crash testing of luminaire supports and shallow-angle corner impacts on guardrail. The crash testing planned in (d), however, was not conducted, hence the need for additional research, with the intention of this testing including luminaire supports and shallow-angle corner impacts on guardrail.
The objectives of this research are the following:
1. Building on test procedures developed under NCHRP Project 22-32, determine appropriate values for RSH performance criteria.
2. Translate research results into a new chapter or supplement in a future MASH edition. These results shall also include recommendations for enhancements to a future RDG edition.
This research shall consider appropriate test vehicles and focus on terminals; however, it shall also consider additional roadside safety devices.
The NCHRP is seeking 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 described in sufficient detail to demonstrate their understanding of the issues and the soundness of their approach in meeting the research objectives.
Project work in NCHRP Project 22-32A shall, with some transitional activity described below, resume where work in NCHRP Project 22-32 left off, as summarized in the Background.
Task 1. Review previous work and literature; recommend updates to work plan.
Task 1a. Review previous work and literature. Review work completed under NCHRP Project 22-32. Conduct a literature review to identify any additional research findings or other technical progress pertinent to the project. Obtain broader technical input on the test procedures recommended in NCHRP Project 22-32 from other experts having experience with them.
Task 1b. Recommend updates to work plan. Based on the findings of Task 1a, recommend any changes felt necessary to the work plan, providing justification. Submit the findings of Task 1a and the updated work plan to NCHRP for approval. NCHRP approval is required before work on Task 2 may begin.
Task 2. Evaluate test procedure effectiveness via crash testing. The research team shall evaluate the procedures recommended under NCHRP Project 22-32 and confirmed in Task 1 for measuring occupant risk factors in side impacts. The testing shall include the following objectives: (a) demonstrate repeatability of the side impact testing; (b) determine the performance of current guardrail end terminals; (c) determine the performance of luminaire poles; and (d) evaluate the vulnerability of current guardrail end terminals to shallow angle impacts. The research team shall ensure that (a) critical MASH Test Level 3 vehicles are considered in the testing; (b) MASH guardrail end terminals are used in the testing; and (c) confidentiality shall be maintained for any proprietary hardware tested, e.g., by categorizing performance issues by nature rather than by specific device characteristics. Following the testing, the team shall submit an interim report summarizing Task 2 results for NCHRP approval. The team shall also present a summary of Task 2 results at an in-person meeting with NCHRP. NCHRP approval of the interim report is required before work on Task 3 may begin.
Task 3. Analyze test results and develop evaluation guide.
Task 3a. Analyze test results. From Task 2 results, determine the practicality of the evaluation criteria and how agencies would implement them. Develop an outline for an evaluation guide. Submit the analysis and guide outline to NCHRP for approval via technical memorandum. NCHRP approval of the memorandum is required before Task 3b can begin.
Task 3b. Develop evaluation guide. Elements for the guide shall include, but not be limited to, technical considerations for public or private organizations conducting the evaluations and implementation considerations for stakeholders, e.g., modifying MASH guidelines.
Task 4. Submit final report and evaluation guide. Submit a final report documenting the entire project and the research team’s recommendations for implementing methods for evaluating side impact testing by the roadside safety community. Submit a standalone comprehensive evaluation methodology guide in a format suitable as a supplement or new chapter in the next MASH edition and as recommended additions to the RDG.
Status: Proposals have been received in response to the RFP. The panel will meet to select a contractor to perform the work