The Roadside Safety Pooled Fund has prioritized their research needs for various hardware systems, including optimizing the geometry of guardrail blockouts. The impact severity associated with MASH crash tests increased in comparison to NCHRP Report 350. This has placed a greater demand on barrier systems that has resulted in failures of some existing W-beam guardrail barrier applications. While the improvements incorporated into the Midwest Guardrail System (MGS) have enhanced capacity, researchers have continued to see W-beam rail ruptures during both small car and pickup crash tests of various guardrail configurations. This can be attributed to the increased demand and different vehicle interactions resulting from the change of test vehicles and impact conditions, including an increase in impact angle in Test 3-11 from 20 to 25 degrees. During recent testing, researchers identified possible impact performance benefits associated with the use of shortened (in the vertical direction) blockouts. These shortened blockouts were most recently successfully implemented in a W-beam guardrail system with half post spacing that had previously failed due to rail rupture in a test with standard length blockout and a thrie-beam guardrail and median barrier system developed through the Roadside Safety Pooled Fund. Further, shortened blockouts have been used for years in thrie-beam transitions to improve vehicle stability. Therefore, there is a need to investigate if improved geometry of blockouts can provide similar enhancements to other W-beam guardrail systems. This project will evaluate improvements to all aspects of blockout geometry and evaluate their impacts on guardrail crashworthiness.

Objective

The primary objective of this study is to optimize guardrail blockout geometry to improve crashworthiness. Improvements to all aspects of blockout geometry will be evaluated, not simply a shortened height. This new optimized blockout will be evaluated in systems which failed MASH crash tests and also in systems which have successfully passed MASH criteria.

Benefits

This project will benefit the members of the Roadside Safety Pooled Fund by providing improved crashworthiness in guardrail systems. Several commonly utilized systems have experienced failed crash tests over the years, and a new optimized blockout may improve their crashworthiness. Ideally, these systems with optimized blockouts would be suitable for implementation as MASH compliant systems.

Products

TTI researchers will provide recommendations for an optimized blockout design. This optimization effort will evaluate various design changes through computer simulation. Subsequently, one MASH 3-10 test and one MASH 3-11 test will be performed. TTI researchers will then prepare and submit a research report fully documenting the work completed within this project. TTI researchers will submit this report to the technical representative of the Roadside Safety Pooled Fund for review and approval.

Work Plan

The work plan for this phase will consist of three tasks. The first task is titled Engineering Review. The second task is titled MASH Crash Testing. The third task is titled Reporting and Documentation.
Task 1: Engineering Review
This task’s objective is to optimize the geometry of the guardrail blockout through computer simulations of vehicular impacts. The first step is to review previous literature and testing. One half of this review will investigate utilizing less common blockout geometry. The other half of this review will investigate the cause of commonly utilized systems failing MASH crash testing. In this effort, the research team’s goal would be to determine a cause of failure and investigate the possibility of improving crashworthiness utilizing a different blockout geometry. The TTI research team will accomplish this review through various means, including use of internet search engines, as well as a review of research and crash testing work indicative of blockout design improvements from authoritative sources such as the Roadside Safety Pooled Fund MASH database, and the Midwest Roadside Safety Facility library of research projects. The TTI research team will review this material to gain insight into possible geometric improvements in order to compile a list of the most promising optimized blockout designs. The TTI research team will then develop finite element analysis (FEA) models of guardrail systems utilizing standard blockoutsidentified in the literature review (both failed and successfully crash tested systems). Subsequently, the TTI research team will use the explicit finite element code LS-DYNA (2) to perform initial impact simulations using the developed barrier models and currently available vehicle models. The TTI research team will compare these initial simulations to previous crash testing to ensure proper predictive capability. If needed, modifications to these models will be made to improve predictive capability. Once the models’ predictive capability has been confirmed, the TTI research team will complete impact simulations with the most promising optimized blockout designs identified above. These simulations will be completed utilizing currently available MASH vehicle models and impact conditions. The TTI research team will evaluate the simulations for crashworthiness concerns for those systems which successfully passed MASH criteria with standard blockouts and for crashworthiness improvements for those systems which failed MASH criteria with standard blockouts.
Task 2: MASH Crash Testing
This task’s objective is to complete full-scale crash testing to evaluate the crashworthiness of the optimized blockouts validated using the work described in Task 1. These tests will be run under conditions set forth in MASH tests 3-10 and 3-11. Hardware systems selected for testing will be chosen in cooperation with the technical representative of the Roadside Safety Pooled Fund.
Task 3: Reporting and Documentation
This task includes the reporting and documentation of the project’s effort. The TTI research team will prepare and submit a research report fully documenting the work completed within this project. This report will be submitted to the technical representative of the Roadside Safety Pooled Fund for review and approval.

Time Schedule

Started: February 2023
Time frame: 15 Months

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October 2, 2025