Road sign grammar (full stop)

Why don't road signs abide by the use of grammar rule?

Just been brought to my attention and it's true, I don't recall seeing a full stop on any of them.

 

^ your bound to be late

 

Oops caught. Thought the smallest room was safe

 

that wunner matter with Pete, he takes his time ya know

 

My thread has become an epic fail

 

zed they are chuckle worthy

 

he is worse with his hair you know

 

Nasal or toe?

 

on yer bonce

toe hair ewwwwwwwwwwwwwwww gross :supsbrew:

 

I like to pull mine with my teeth