How to hack digital road signs

You know those digital signs by the side of the road telling us about road conditions or that we should prepare to stop or that our local bridge might be closed next Tuesday from noon to midnight?

Yeah, well, they're pretty easy to reprogram to say much funnier things, like, say, "Zombies Ahead."

According to

This is the internal display system of an Addco sign, according to i-hacked.com.

(Credit: i-hacked.com)