MASH 4-12 Evaluation of a Fence Mounted System for Attachments to Concrete Bridge Barrier

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Problem Statement

Roadside concrete barriers are used by Departments of Transportation (DOTs) as permanent
solutions for providing protection for errant motorists. Typically, the crashworthiness of these
barriers is tested and evaluated through full-scale crash testing conducted per current roadside
safety device standards. Occasionally, DOTs need to mount chain link fences on top or to the
side of these barriers to serve different purposes. When DOTs attach these fences to safety
barriers, the crashworthiness of the entire system needs to be evaluated per current standards.

In 2018, the Roadside Safety Pooled Fund prioritized an evaluation effort of a similar TL-4
median barrier with a fence mount on top. In this effort, readily available chain-link fences
designs were incorporated into the tested system. The installation passed MASH test 4-11 but
failed test 4-12. Therefore, this new project is aimed at evaluating a chain-link fence and
concrete barrier combination with MASH test 4-12.

The purpose of this research is to evaluate the crashworthiness of a chain link fence system
attached to a 36-inch-tall concrete single slope roadside barrier to MASH test 4-12 criteria. The
project will use previous testing, engineering analysis, computer simulation, and full-scale
testing to evaluate this system to MASH test 4-12. (1)

Background

In 2018, the Roadside Safety Pooled Fund prioritized an evaluation effort of a similar TL-4
median barrier with a fence mount on top. This effort evaluated a chain-link fence system
mounted on top of a 36-inch-tall single slope median barrier. The chain-link fence design was
developed from readily available standards and hardware. While no computer simulation was
involved, a rigorous engineering analysis was completed. This included a large effort
investigating previous testing and estimating the amount of interaction of the test vehicles and
the chain-link fence.

In MASH test 4-11, the test vehicle was safely contained and redirected. All MASH criteria were
met. In MASH test 4-12, the test vehicle impacted the barrier and rolled laterally towards the
fence. The interaction with the chain-link fence caused significant damage to the test vehicle, and
the excess damage failed to meet MASH criteria.

In this project, the research team will develop a chain-link fence system to be attached to a 36-
inch tall single slope roadside barrier. This fence will likely incorporate a curved top portion,
which is a common design detail found among DOT standards for chain link fence applications
for railroad tracks. This fence and concrete barrier system will be evaluated to MASH test 4-12

Objective

The project goal is to develop a chain-link fence attached to a roadside concrete single slope
barrier which is crashworthy for MASH test 4-12.

Benefits

The project results will provide Roadside Safety Pooled Fund with a MASH test 4-12 compliant
chain-link fence and concrete barrier option.

Products

The TTI research team will provide video and photographic documentation of the crash tests and
a final report documenting the research and testing performed. TTI research team will further
provide drawings of the barrier system and of each of its components.

Work Plan

The research work plan consists of four tasks as detailed below.

Task 1: Design and Simulation
The TTI research team will review and analysis of previous test results and use engineering
analysis and computer simulation to develop a 4-12 system to be crash tested.

Task 2: Construction
The TTI research team will construct the developed system in the previous task to be crash tested
under MASH TL-4 criteria.

Task 3: Full-Scale Crash Test 4-12
A full-scale crash test will involve a 22,000-lb single unit truck impacting the rail at 56 mph
nominal speed and at nominal orientation of 15 degrees relative to the roadway. The test will be
assessed according to MASH evaluation criteria. It should be noted that MASH TL-4 criteria also requires testing with the small passenger car vehicle (1100C vehicle) and pickup truck vehicle (2270P vehicle). However, the pickup truck test was successfully conducted under the 2018 project referenced previously. For this specific barrier, there is no need to conduct small car test (it’s not the critical test).

Task 4: Reporting
The TTI research team will generate a final report of the research findings. The report will
include drawings of the tested system and of each of its components.

REFERENCES

1. AASHTO, Manual for Assessing Safety Hardware. American Association of State
   Highway and Transportation Officials, Washington D.C., 2002.
2. Silvestri Dobrovolny, C., Kovar, J., Menges, W.L., Schroeder, W., Griffith, B.L., Kuhn,
   D.L., “MASH TL-4 Concrete Median Barrier with Fence Mounted on Top”, Roadside
   Safety Pooled Fund, Report No. 613131, College Station, Texas.