Unh, Carl, I was thinking more along the lines of a big comma, maybe an apostrophe or two, even some hyphens. Reflective vinyl would stand out really well.
I suppose I could find SSS stickers -- but it'd be something like "Punctuation and Spell-check by Seldom Seen Slim" on the vehicles. Okay by you?
PS Yes, I'd make sure the comma is safety-wired.