The British Museum in London is one of the biggest tourist attractions as well as a popular destination for school trips. At the rear entrance, where most busses arrive and park, two giant lions provide a great climbing opportunity for waiting children.
I am not aware of any accidents, but not wanting to take any chances, the management has recently put up signs warning climbers of a deep drop behind the lions. The signs come twofold: one is fixed to the stone wall, simply warning of the deep drop, the other is a non-permanent notice placed closer to the entrance, specifically mentioning the lions. My guess is that the permanent signs were not very successful, and thus the larger, mobile signs were added.

The permanent signs are indeed quite tame; small, dark green plaques, neatly placed along the wall in regular intervals. They feature white type set in a clean sans serif, using line breaks to replace punctuation. The interesting bit is the illustration of an adult male stumbling over what looks like those reversed u-shaped metal stands where you chain your bicycle to. Although it tries to imitate the cross-sectional shape of the wall, it is much too small and does not appear solid. Furthermore, the most important bit, the deep drop, is not pictured. Instead, the baseline of the last line of the warning text creates an invisible horizontal line to the wall section, suggesting a maximum drop of about a foot in relation to the stumbling man.
In the end, we have a polite, dark green sign, kindly reminding adults not to stumble over small boulders. No wonder the kids ignored it.
The mobile signs improved the situation only slightly: the wall section is now solid, but has not increased in size. The stumbling figure is still an adult and not a child, and both hover in white space, no deep drop in sight. The warning text includes the climbing the lions part, but now has a massive leading and appears too small. A further addition is the French translation. Apparently, only English and French people are climbing the lions. German, Spanish, and Japanese tourists are welcome to fall and break their necks.
Warning signs and politeness don’t go together. Avoiding injuries or a pretty facade? Make a decision. A better illustration would not need any translation.