Watch this.
A heavy vehicle departs its lane and impacts a central barrier. There is little to no median here, so the barrier becomes the primary defence against a crossover into the opposing carriageway.
This is exactly the scenario the system needs to manage. Barriers are not about preventing the crash, but about containing and redirecting the vehicle to avoid a high severity head on outcome.
How well it performs comes back to the barrier Test Level. That is the severity of crash the barrier is expected to safely manage.
This is a risk-based engineering decision with understanding of the testing protocol (MASH in Australia and New Zeeland). But speed, traffic volume, heavy vehicle percentage, lateral clearance, and the consequence of a breach all need to be considered.
High volume roads with large proportions of heavy vehicles and minimal or no median sit at the higher end of the risk spectrum. But there are many variables that influence the decision.
That’s why most jurisdictions are not highly prescriptive with Test Level requirements.
The question is not “what is the standard Test Level?”, it’s “what level of containment is needed here to manage the actual risk?”
There’s always lots of good discussion about Test Level selection in the 𝗥𝗼𝗮𝗱 𝗦𝗮𝗳𝗲𝘁𝘆 𝗕𝗮𝗿𝗿𝗶𝗲𝗿 𝗰𝗼𝘂𝗿𝘀𝗲. Next one coming up in 𝗦𝘆𝗱𝗻𝗲𝘆 𝘀𝘁𝗮𝗿𝘁𝗶𝗻𝗴 𝟮 𝗝𝘂𝗻𝗲.
P.S. Have a look at the vehicle roll in this crash. It’s a good example of why Working Width includes a roll allowance.
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