ISSOM 2007 wrote:524 Impassable fence or railing
An impassable fence or railing, which shall not be crossed, due to forbidden access or because it may constitute a danger to the competitor because of its height.
ISSprom 2019 wrote:518 Impassable fence or railing
An impassable fence or railing shall not be crossed, due to danger to the competitor or because of its height.
Apart from the renumbering of the symbol, the phrase "due to forbidden access" has now been removed, and from similar symbols too, e.g. walls and hedges.
So, if you have to indicate that a low fence is impassable because of forbidden access, it seems you have to do this with the purple overprint (708) instead ...
I can see the logic in letting mappers just focus on height/danger when surveying and leaving it to subsequent organisers/planners to indicate when something is impassable due to forbidden access - the latter is something which can change from time to time and also might require a lot of effort to find out about.
But I’m not sure that the use of a purple overprint answers the question. Whilst this might work well in forest terrain on ISOM maps, where impassable fences etc will normally be well separated, an ISSprom map with a lot of impassable walls/fences/hedges will look very purple-cluttered.
There may also be parts of the terrain where these features are so close together that the purple overprinted lines merge, making this not an ideal solution.
What do others think? Especially from a non-mapping point of view!