The use of funny and quirky messages on electronic signs will be against the law on America’s highways. The U.S. Federal Highway Administration, a division of the Department of Transportation, issued a sweeping set of guidelines last month “to improve safety for pedestrians, bicyclists, and all road users.” Part of the new 1,100-page manual regulates electronic traffic signs and other traffic control devices, which will no longer be allowed to post humorous messages that could distract drivers or be misunderstood. Messages with obscure meanings and references to pop culture will also be banned…