Introducing MASH
Background
In 2018, the Austroads Safety Barrier Assessment Panel (ASBAP) advised industry of an important change to the eligibility criteria for safety product submissions. Previously, submissions to the Panel were based on crash testing in accordance with NCHRP Report 350 in line with AS/NZS 3845:1999.
The updating of AS/NZS 3845 in 2017 recognised the introduction of the MASH crash test standard. Therefore, the Panel adopted MASH guidelines for all new product submissions including steel guardrails, concrete barriers, wire rope safety barriers, end terminals, crash cushions and transitions.
Who is ASBAP
ASBAP assesses the crashworthiness and suitability of road safety barriers, systems and devices for deployment on roads managed by Australian/New Zealand transport agencies. The following jurisdictions participate in the Panel assessment:
- Transport for NSW
- Department of Transport, Victoria
- Department of Transport & Main Roads, Queensland
- Department of Planning, Transport & Infrastructure, South Australia
- Main Roads Western Australia
- Department of State Growth, Tasmania
- Department of Infrastructure, Planning & logistics, Northern Territory
- Territory & Municipal Services, Australian Capital Territory
- New Zealand Transport Agency
The Panel undertakes a technical and risk assessment to determine the suitability of the road safety barrier. The assessment includes analysis of full-scale crash testing and supporting documentation provided by the proponent to ensure correct and safe deployment of the system. The Panel supports the Safe System philosophy and the minimisation of harm for all road users.
What is MASH?
The AASHTO Manual for Assessing Safety Hardware (MASH) is an update to and supersedes NCHRP Report 350 for the purposes of evaluating new safety hardware devices and is the basis of crash testing as stated in AS/NZS 3845.1 Road Safety Barrier Systems. The introduction of MASH follows changes to the vehicle fleet, researching of real-life impact conditions and updated criteria for evaluating barrier performance.
MASH presents uniform guidelines for the crash testing of both permanent and temporary highway safety features and recommended evaluation criteria to assess test results. Guidelines are also presented for the in-service evaluation of safety features. These guidelines and criteria, which have evolved over the past 40 years, incorporate current technology and the collective judgment and expertise of professionals in the field of roadside safety design.
What are the differences between MASH and NCHRP Report 350?
Major differences between MASH and NCHRP Report 350 include:
- changes to the test vehicles,
- changes to the number and impact conditions of the test matrices,
- changes to the evaluation criteria, and
- addition of new features to the test guidelines.
What is the underlying Philosophy of MASH?
The underlying philosophy in the development of the MASH guidelines is that of “worst practical conditions.” When selecting test parameters, such as the test vehicle, impact speed and angle combination, point of impact, test matrix, etc., every effort is made to specify the worst, or most critical, conditions.
For example, the weight of the small passenger car test vehicle was selected to represent approximately the 2nd percentile of passenger type vehicles, i.e., only two percent of vehicles weigh less than the specified test weight. The impact speed and angle combination represents approximately the 93rd percentile of real-world crashes, i.e., only seven percent of crashes are more severe. When the combined effects of all testing parameters are considered, the testing represents the extremes of impact conditions to be expected in real-world situations. It is also implicitly assumed that, if a roadside safety feature performs satisfactorily at the two extremes, then the feature would also work well for all impact conditions in between. This assumption has shown to be reasonable for most roadside safety features.
Examples of MASH Compliant Barriers
Safe Direction is an Australian manufacturer of safety barrier systems. Our in-house design team combined with our superior technical expertise has been responsible for the development of numerous ASBAP approved, MASH compliant guardrail safety barrier systems. Our product range includes:
- RamShield W-Beam Guardrail, MASH TL3 complaint
- RamShield Low Deflection, MASH TL3 complaint
- HammerBeam Culvert Barrier, MASH TL3 complaint
- MSKT W-Beam Terminal, MASH TL3 complaint
- RamShield High Containment, MASH TL4 complaint
- CrocGuard Culvert Barrier, MASH TL4 complaint
How do Guardrail Barriers work?
A guardrail barrier features a steel beam supported by steel posts. The flexural strength of the beam provides safe vehicle containment and redirection as it deflects and releases from the posts. The posts are designed to yield when impacted by the errant vehicle by bending proximate to ground level.
The steel beam may feature a w-beam or thriebeam guardrail, depending upon the desired vehicle containment level and the available space between the barrier system and the roadside hazard. Safe Direction guardrail barriers feature a RamShield tab, designed to control the release of the steel beam from the supporting posts and facilitate safe vehicle containment.
How do I choose a MASH complaint barrier?
Safety barrier systems and products assessed and recommended for acceptance by ASBAP are issued a Technical Conditions for Use. These documents are published by participating road agencies.
When selecting a MASH compliant roadside barrier designers should consider the following:
- Design vehicle,
- Design speed,
- Available distance between the barrier and roadside hazard,
- Ground conditions,
- Ease of installation and repair, and
- Technical support.
Safe Direction welcomes all road safety barrier product enquiries and is pleased to provide design guidance.
