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Each barrier system tested to EN 1317 is awarded a working width class. This is calculated by adding the width of the barrier plus the amount of deflection that occurs when the barrier is impacted to the test criteria. The barrier’s deflection is measured from the traffic face of the barrier.

So, for example: For a barrier with a working width of W1, the total barrier dynamic deflection combined with the barrier width will not exceed 600mm, whereas a barrier with a performance level of W3 will not exceed 1000mm.

Containment levels are determined through impact tests where a vehicle of a specified mass and speed is driven into a barrier. The barrier’s performance is assessed based on factors like:

• Vehicle penetration: Whether the vehicle breaks through the barrier.
• Vehicle trajectory: The path the vehicle takes after impact.
• Occupant risk: The level of risk to the vehicle occupants.

Several factors influence the choice of containment level, including:

• Speed limit: Higher speed roads require higher containment levels.
• Traffic volume: Roads with heavy traffic may need a higher containment level.
• Roadside environment: The presence of hazards like steep slopes, water bodies, or structures will influence the required level.
• Vehicle type: Heavier vehicles require barriers with higher containment levels.