GVB signs

A good sign in a public place immediately and unambiguously communicates its meaning. A picture of a burning cigarette with a red stripe or cross through it can hardly be understood otherwise.
Here's a selection of signs from the GVB, the Amsterdam public transport system, and what I think they should mean.

	Tickets Buy one ticket: cool. Buy two tickets "just to be sure": even cooler. Thanks!
	Bikes By all means, bring your bike.
	No bikes Oh wait, on second thought, it's prohibited.
	Rollerblading on a skateboard Don't try to rollerblade on a skateboard. No one has ever managed that.
	Dog shit This is Amsterdam. You're gonna step in dog shit. But don't use our seats to get it off.
	No free jazz improv Don't bring along a kiddie trumpet when you take your boombox. It's annoying.
	Diet You shouldn't be eating and drinking all this junk.
	Safety check Do not use strollers that "levitate" and are made from toothpicks. And save that baseball cap until your kid is big enough for Little League.