Disturbing and/or Amusing Sign Dept.

This flashing sign is on the Causeway, a 23-mile-long bridge going north out of New Orleans. The world's longest bridge over a body of water. Also, note Project:Bomber parked behind the sign. But I digress...

First, the sign flashes a friendly reminder to drive safely...

 

Then the sign changes to admonish us not to read while driving. Now, if I didn't read the sign, how would I know not to read while driving? And if I knew not to read while driving, who is this sign for? My passengers? But, they're not driving, so... nevermind.