There are some guidelines for the messages. The signs have three lines and 18 characters, including spaces per line, hashtags, phone numbers and website addresses won't be allowed and signs can't handle emojis.
The contest runs until Feb. 19. After that, ADOT will go through the submission and select 15 of the best ones to advance to the next round. Next month, the agency will post the finalists on its website and let the public pick the winner.
The winning message will appear on Dynamic Message Signs for two days in April.
ADOT started displaying the unconventional safety messages on overhead signs more than a year ago. It was in an effort to fight the social acceptance of impaired driving, distracted driving, speeding, aggressive driving and other dangerous driving behaviors, ADOT said.