It is a sign of the times that such a warning is considered necessary. Twenty years ago all people in wheelchairs had to exercise bladder control worthy of the Royal Family; planning had nothing to do with it, there just weren't any accessible loos. You went before you left home, you didn't drink while you were out and you hung on until you got back.
In these more enlightened times all new public buildings have to provide toilets for the disabled. Nevertheless it is a serious mistake to assume that it is now possible to relieve oneself without difficulty.
First you've got to find the disabled toilet. It may be on the other side of the building from the ordinary toilets or it may be unmarked. It may be necessary to take a lift or to go through the kitchens. The unisex disabled toilet may even be located inside the ordinary Ladies, which is probably marginally less disconcerting to all concerned than being located inside the Gents. On the other hand, the toilet may open directly off the foyer, without even an airlock.
It is not unheard of for the management to use the disabled toilet to store cleaning supplies or odd bits of furniture. This is not necessarily a problem, as the disabled toilet is often located in the highly irregular space left over after rectangular toilet facilities have been fitted into a strangely shaped piece of modern architecture.
Doors usually slide, but it is possible to encounter a door that swings inwards so that there is no room to close it because the wheelchair is in the way. Once inside, something is always wrong. One popular set of specifications recommends raising the pedestal to a height that is inconvenient for most people; this is often combined with a handbasin placed so close to the toilet that you can wash your hands while still aboard, but which makes approaching the seat from the front quite impossible. The self-activating hot-air dryer may be located so low and so close to the toilet that it runs non-stop from the moment you first reach for the handrail. There is usually no shelf on which to put your comb and makeup, a matter of academic concern since the mirror will be too high to be of use. Paper towel dispensers and coathooks are often out of reach, while provision of facilities for sanitary napkin disposal is still sometimes overlooked.
Disabled toilets are not for the fainthearted, as they almost never have a lock on the door - there won't even be a sign to indicate vacancy or occupation. Privacy, it seems, is for the ablebodied.
This strange attitude reaches its purest form of expression at the National Gallery of Victoria. Here there are disabled loos for both sexes, and just as well. In each case the airlock opens into a spacious room containing two handbasins, two mirrors and two toilets; all in the one room, no partitions, no curtains and, of course, no lock on the door.
On the positive side, disabled toilets are always remarkably clean and almost never out of soap or paper. This is undoubtedly because, although there is no reason at all why they shouldn't, ablebodied people never use them. Can't think why....