No, really… a long time ago, I knew a person who knew a person who designed freeway signs, the exit sign in particular, and it was called a freeway exit sign.

;-} Could call it a “smoker’s warning” or something I guess, but why complicate the simple.

As a graphic symbol, the technical name for these is ideographs or ideograms.

Quote:

A character or symbol representing an idea or a thing without expressing the pronunciation of a particular word or words for it, as in the traffic sign commonly used for “no parking” or “parking prohibited.” Also called ideograph.

End of Quote.

Source of quote:

http://www.tfd.com/ideograms

They are also called symbol signs, and perhaps environmental signs.

These are to be differentiated from logograms, defined as:

Quote:

A written symbol representing an entire spoken word without expressing its pronunciation; for example, for 4 read “four” in English, “quattro” in Italian.

End of quote.

Source:

http://www.tfd.com/logogram

A “logo” is an image made from letters, MacDonald’s big M and NASA’s toothpaste logo* being two of them.

There are groups and committees around the world which look after adopting standard designs for such symbol signs, and one is at this link:

http://www.aiga.org/content.cfm/symbol-signs

Presumably there is a world body or association for these volunteer groups.

*Trivia: In 1960 a graphic designer named Allan Fleming was hired to create a new logo for CN Rail in Canada. He was having a great deal of trouble coming up with ideas, and the deadline for his presentation was drawing near. One morning he got up, and was in quite an agitated state when he went to brush his teeth. Shaking, he squeezed the tube too hard and a squiggle of toothpaste landed on his sink. Looking at it, he realized the squiggle sorta looked like a letter, so he squeezed out a new logo for the letters CN and realized this was what he was looking for.

This style of lettering is also called spaghetti writing.

CN Logo here:

http://www.cn.ca/about/company_information/history/en_Aboutlogo.shtml

It may not have the same name from country to country and could vary within, choose what the locals prefer and you can’t go wrong.

I hope this helps.