Don't ever underestimate the power of a smiley face. The council of South Lanarckshire in Scotland added a simple face to road signs that tell drivers their speed: smiley face if they're under the speed limit and sad face if they're over.
That simple addition resulted in the numbers of speeders being reduced by 53%: Link - via Barking up the wrong tree
So, it's illegal to text while you drive, but legal for the sign to text you while you drive.