My uncle has been involved in a project installed Variable Message Signs ( VMS ) around NZ. The VMS display messages about road conditions such as certain passes being closed by snow, chains being required or high winds, that sort of thing. For his birthday a year or so back I did something similar to this for a birthday card by editing a photo of one of the signs in Photoshop to look like it was saying Happy Birthday. He showed it to a few people involved in the project and eventually a scan of it made its way to one of the top guys in the project. He actually thought my uncle had got someone to put the message on the sign and some quick talking had to be done to convince him it was just a doctored photo :-). Eventually he clicked when some pointed out the text was 7 rows high instead of the 6 they use on the signs, something like that anyway. Disaster averted, jobs safe :-).
Regards,
Jo