Yearly winter storms will seek out the seriously understrength, but it is the occasional freak winds—only seen every 10 to 20 years—which can wreak havoc”
Wind can produce unexpectedly large loads. For instance, if you turn a totem style sign horizontally, severe storms produce a load on the face of the sign that is equivalent to two large people standing on every square metre. It is these loads that British Standards are designed to cater for.
We all buy cars or fly in planes with expensive safety features which are there just in case —why should signs be any different when peoples safety is at stake?”
However, both Standards attempt to provide a method of calculating worst-case conditions using the most appropriate criteria. This should mean that a sign designed to a Standard would withstand a very severe storm, only likely to happen once every 10 to 20 years. In other words, it reduces risk of failure to a much smaller percentage than would otherwise be the case.