MASH Compliant
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. MASH is also the basis of testing procedures for road safety systems as stated in AS/NZS 3845.1: 2015 Road Safety Barrier System and Devices. The introduction of MASH follows changes to the vehicle fleet that has increased in weight and height.
The MASH crash testing guidelines evaluate the impact performance of permanent and temporary highway safety features. Performance is evaluated in terms of the risk of injury to occupants of the impacting vehicle, the structural adequacy of the safety feature, the exposure to workers and pedestrians that may be behind a barrier or in the path of debris resulting from impact with a safety feature, and the post-impact behaviour of the test vehicle.
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.
The MASH evaluation guidelines cover both permanent and temporary highway safety features, including:
- Longitudinal Barriers
- Flexible and semi-rigid barriers
- Rigid barriers
- Barrier transitions
- Guardrail End Terminals
- Crash Cushions
- Redirective
- Non-redirective
- Support Structures
- Breakaway signs
- Utility poles
- Work-zone traffic control devices
- Workzone Attenuation and Channelisers
- Truck-mounted attenuators (TMAs)
- Longitudinal channelizers
- Other Devices
- Traffic gates
- Arrestors
- Drainage and Geometric Features
Guardrail Barriers are steel, longitudinal barrier systems designed to contain and redirect errant vehicles away from roadside hazards. Guardrail barriers feature steel posts supporting w-beam or thrie-beam guardrail.
Guardrail Terminals are installed at the ends of the longitudinal guardrail safety barrier system to mitigate the risk of impacts at the end of the system and to anchor the system facilitating safe vehicle containment and redirection.
Bridge & culvert barriers are specifically designed to provide safe vehicle containment and redirection when installed along the edge of an elevated structure.
Crash cushions are installed to shield the blunt ends of safety barrier systems. They are designed to decelerate an end-on vehicle impact over a short distance and feature energy absorbing cartridges or components.
Wire rope safety barrier systems rely upon the tensile strength and deflection of wire cables to contain and redirect errant vehicles. They provide stable vehicle containment and low ride-down decelerations.
Workzone Barriers are used as part of the traffic management plan to protect roadside workers and guide motorists through the construction zone. and are designed for rapid deployment and removal.
Frequently Asked Questions
Who is AASHTO?
The American Association of State Highway Transportation Officials (AASHTO) provides guidance related to the design and installation specifications of roadside hardware and safety hardware.
What is the purpose of MASH?
The AASHTO Manual for Assessing Safety Hardware (MASH) presents uniform guidelines for crash testing permanent and temporary highway safety features and recommends evaluation criteria to assess test results. MASH is recommended for highway design engineers, bridge engineers, safety engineers, maintenance engineers, researchers, hardware developers, and others concerned with safety features used in the highway environment.
Why was MASH developed?
MASH is an update to and supersedes NCHRP Report 350. The introduction of MASH follows changes to the vehicle fleet that has increased in weight and height.
What are some of the differences between MASH and NCHRP Report 350?
Some of the major differences between MASH and NCHRP Report 350 include Changes in Test Matrices, Changes in Test Vehicles, Changes in Test Installations, Changes in Evaluation Criteria, Changes in Test Documentation and Changes in Performance Evaluation.
What are the Changes in Test Vehicles?
The small passenger car has increased from 820kg to 1100kg. The pick-up truck has increased from 2000kg to 2270kg. The single unit box truck has increased from 8000kg to 10,000kg.
What are the main Changes in Test Matrices?
The small car impact angle is increased from 20 to 25 degrees. The impact speed for the single-unit truck test is increased from 80 km/h to 90 km/h. The impact angle for length-of-need testing of terminals and crash cushions is increased from 20 to 25 degrees to match that for longitudinal barriers. The impact angle for oblique end impacts for gating terminals and crash cushions is reduced from 15 to 5 degrees.
What are the MASH Test Levels?
Longitudinal barriers may be tested to six test levels and other roadside features may be tested to three test levels. A test level is defined by impact conditions (speed and angle of approach) and the type of test vehicle (ranging in size from a small car to a fully loaded tractor-trailer truck).
The first three test levels are limited to passenger vehicles while the last three incorporate some form of heavy truck. Note that longitudinal barriers are the only safety features for which all six test levels are applicable.
What is “worst practical condition”?
For impact speed and angle, the “worst practical condition” has been traditionally set at the 85th percentile level. Test vehicles are normally selected based upon vehicle body style and weight. Weights have generally been selected to approximate the 2nd and 90th percentile levels for passenger vehicles. Impact locations on a safety feature are often selected to represent a critical impact point (CIP) that creates the greatest probability of test failure. Hence, the combination of 85th percentile impact speed, 85th percentile impact angle, 5th and 95th percentile vehicle weights, and critical impact point is believed to represent a worst practical condition.
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.
Is MASH used for the evaluation of safety barriers deployed in Australia?
Yes. MASH compliance commenced 1 January 2020 throughout Australia. The Austroads Safety Barrier Assessment Panel (ASBAP) assesses the crashworthiness and suitability of road safety barriers, systems and devices for deployment on roads managed by Australian/New Zealand road agencies in line with AS/NZS 3845.
AS/NZS 3845 nominates MASH as the current basis for crash testing protocol.
Am I required to replace safety barrier hardware that does not comply with MASH?
Typically, State Road Agency guidelines do not permit installations of permanent safety barrier products with a legacy status. Safety barrier systems with a legacy status continue to provide the level of service at which they were originally tested. Legacy status products may be maintained and/or repaired until the end of their service life, or when parts are no longer available. When long lengths of legacy items are damaged or within the limit of works, an assessment should be made on whether an approved system may be installed instead as part of reinstatement works. Legacy products shall not be relocated.
