That may be intentional. Road signs typically see lots of usability research (do drivers recognize this when driving past it at 50 mph in fog?) before they are deployed, and a modern camera is just a box.

I once read that one country decided to keep the steam train on their road signs based on such results because it makes it easier to distinguish it from other signs.

Edit: https://www.quora.com/Who-designs-the-icons-on-the-UK-road-s... claims this was indeed intentional.