EN 1317, AASHTO M180 & AS/NZS Standards Explained

Highway guardrails are an essential part of modern road safety infrastructure. They are designed to redirect vehicles, reduce the severity of run-off-road crashes, and protect motorists from roadside hazards such as steep slopes, fixed objects, bridges, and opposing traffic.

However, not all highway guardrails are manufactured or evaluated according to the same requirements. Different markets use different standards and testing systems to determine whether a road safety barrier is suitable for a particular application.

Among the most widely referenced standards are EN 1317 in Europe, AASHTO M180 in the United States, and AS/NZS standards in Australia and New Zealand.

EN 1317: European Standard for Road Restraint Systems

EN 1317 is the European standard series covering road restraint systems. It provides a framework for evaluating and classifying roadside safety barriers, vehicle parapets, terminals, transitions, and other restraint systems.

Unlike a material specification that focuses primarily on steel composition or dimensions, EN 1317 places significant emphasis on the performance of the complete restraint system under impact conditions.

What Does EN 1317 Cover?

The EN 1317 series addresses different aspects of road restraint systems, including:

• Vehicle restraint systems
• Containment performance
• Impact severity
• Working width
• Vehicle intrusion
• Crash testing
• Terminals
• Transitions
• Performance classification

One important feature of the EN 1317 approach is that barriers are classified according to their tested performance rather than simply being described by their physical dimensions.

EN 1317 Containment Levels

Highway barriers tested under EN 1317 can be classified into different containment levels depending on their performance during crash tests.

Common classifications include:

• N1
• N2
• H1
• H2
• H3
• H4a
• H4b

The appropriate containment level depends on factors such as road design, traffic conditions, vehicle types, roadside hazards, and the consequences of a vehicle leaving the roadway.

For example, a barrier designed primarily for passenger vehicles may not provide the same containment performance required where heavy commercial vehicles are common.

Working Width

Another important EN 1317 parameter is working width.

Working width describes the maximum lateral distance that a barrier system occupies during an impact, including the dynamic movement of the barrier.

This is particularly important when there are fixed objects, steep slopes, structures, or other hazards immediately behind the guardrail.

Therefore, selecting a highway guardrail based only on containment level is not sufficient. Engineers should also consider working width and other tested performance characteristics.

AASHTO M180: Highway Guardrail Steel Components

In the United States and many international markets influenced by U.S. highway specifications, AASHTO M180 is an important specification for highway guardrail components.

The current AASHTO M180 specification is titled “Standard Specification for Steel Components for Highway Guardrail.” It covers steel components used in non-proprietary highway guardrail systems, including guardrail beams, transitions, end sections, fasteners, posts, and anchorage components.

This distinction is important:

AASHTO M180 is primarily a material and component specification, while crash-performance requirements are addressed through separate safety-hardware evaluation procedures.

What Does AASHTO M180 Cover?

Depending on the applicable edition and component, AASHTO M180 addresses items such as:

• Corrugated steel guardrail beams
• W-beam guardrail
• Transition beams
• End sections
• Buffer sections
• Terminal connectors
• Backup plates
• Steel posts
• Bolts, nuts, and washers
• Wire rope and fittings
• Protective coatings
• Material and manufacturing requirements

The specification also addresses different types of corrosion protection and requirements related to coating, storage, and handling.

Why Is AASHTO M180 Important?

A highway guardrail must maintain its structural properties in demanding outdoor environments. Roadside barriers are exposed to:

• Rain
• Humidity
• Road salt
• Temperature changes
• UV exposure
• Vehicle impacts
• Construction and maintenance activities

AASHTO M180 helps establish consistent requirements for the steel components used in highway guardrail systems.

AS/NZS Standards for Highway Guardrail

Australia and New Zealand use their own framework for road safety barriers, centered on the AS/NZS 3845 series.

AS/NZS 3845 addresses road safety barrier systems and devices and covers areas such as system requirements, crash testing, installation, maintenance, and assessment. Austroads notes that AS/NZS 3845 is used together with AASHTO’s Manual for Assessing Safety Hardware (MASH) in the assessment of road safety hardware for the Australasian market.

The current framework includes:

• AS/NZS 3845.1:2015 – Road safety barrier systems
• AS/NZS 3845.2:2017 – Road safety devices

These standards superseded parts of the earlier AS/NZS 3845:1999 framework.

AS/NZS 3845 and Crash Testing

AS/NZS 3845 establishes requirements for road safety barrier systems and includes crash-testing requirements used to establish the suitability of a system.

This means the evaluation is focused on the performance of the barrier system rather than simply whether a particular W-beam has the correct dimensions.

For projects in Australia and New Zealand, engineers and contractors may also need to consider local road-agency requirements and accepted-product lists.

For example, New Zealand’s Waka Kotahi road safety barrier specifications require accepted safety hardware systems for state highway applications, with the relevant framework referencing AS/NZS 3845 and MASH.

EN 1317 vs AASHTO M180 vs AS/NZS 3845

Although these standards are often mentioned together when discussing highway guardrail, they do not serve exactly the same purpose.

Standard	Main Market	Primary Focus	Typical Application
EN 1317	Europe and markets using European standards	Road restraint system performance and classification	Crash-tested vehicle restraint systems
AASHTO M180	United States and international projects using AASHTO specifications	Steel guardrail components and materials	W-beams, posts, fasteners and related components
AS/NZS 3845	Australia & New Zealand	Road safety barrier systems and devices	Barrier design, assessment, testing and installation

Why Crash Testing Matters for Highway Guardrail

A highway guardrail is a safety system, not simply a steel product.

During a vehicle impact, the guardrail must absorb and redirect energy in a controlled manner. The system may deform, posts may rotate or pull out, and the rail may deflect laterally.

A successful barrier should help prevent the vehicle from:

• Leaving the roadway
• Passing through the barrier
• Vaulting over the barrier
• Penetrating the barrier
• Re-entering the traffic stream in an unsafe manner
• Creating excessive risk for vehicle occupants

Conclusion

EN 1317, AASHTO M180, and AS/NZS 3845 are important standards for highway guardrail, but each focuses on different requirements. When selecting guardrail, consider the applicable standard, crash performance, material specifications, and installation requirements to ensure a safe and compliant barrier system.