All the signs are marked as public domain or with a CC license on wikipedia. So you definitely wont have to buy the standard.
If you are producing warning signs for selling you might want to buy it to get the true colour data etc.
If you are producing warning signs for selling you might want to buy it to get the true colour data etc.
It's not obvious to me that (under US law) these are copyright protected. It may be a similar case as typefaces vs. fonts. The language on the ISO website suggests, at least to me, that you are paying for particular files in particular formats and are not licensing a protected symbol. Also the language in the ISO standards describes abstract symbols, and afaik there is no normative requirement to use the exact images from the standard / ISO to be compliant.