Moving message sign for cars?

Question

In the most recent series of Top Gear, the episode where jeremy, james and Richerd went on the camping holiday, they stopped off at a garage and Jeremy bought an electronic moving message board/sign, which allowed him to type messages on it which were then displayed for other drivers to see and scrolled horizontally. Does anyone know where you can get hold of one of these and how much roughly they cost. also are they road legal. thanks.

Answer 1

They are available at electronics places, usually in kit form:

http://www.apogeekits.com/scrolling_marquee.htm

You see cabs with these things all around, I don't see why they would be illegal (but I don't know for sure).