When road signs bemuse

Far be it for me, a mere colonist, to quibble with the way the English use English. But this road sign in Bristol distracted me so much that I nearly hit a parked car:

Are they zombies?

Somebody in the city government proposed this sign.

            Worker:     "Pardon, guv'nor, maybe we should use, 'Dead Slow Children'?"

            Boss:         "Well, Nigel, let me give it a think. What are our other options? I need to make sure we bloody hell
                              don't do a cock up."

            Worker:     "Me and my mates have been working on this for a fortnight. We're knackered. If we have to go
                              back to the drawing board it'll all go to pot. We think 'very slow' is rubbish. Doesn't pop, y'know?
                              'Extremely slow' was too bloody long. And those 'Twenty's Plenty' signs are poufy, amiright?"

            Boss:         "Cheerio! 'Dead Slow Children' is scrummy. Any punctuation we could use to make it more clear?"

            Worker:     "Blimey, what is 'punctuation'?"