The symbol acts as shorthand for drivers. It's meant to alert contacts that the person they're trying to reach is soon to be driving, and won't be available to chat. The code was created as part of AT&T's "It Can Wait" campaign, which encourages drivers to put the phone down and keep their eyes on the road.
The telecommunications giant set up a website where users can create gif memes of ridiculous messages they've received from behind the wheel, see which celebrities on Twitter have posted the hashtag and take a pledge to abstain from texting and driving. So far, people from country music artist Tim McGraw to the Arkansas Attorney General have tweeted the tag. Altogether, five million people have joined the pledge, according to CBS News.
The fight against texting while driving has been taken up by private companies and federal safety regulators alike. The Department of Transportation came out with a chilling ad this year warning drivers, especially younger ones, of the dangers of distractions behind the wheel. The public service announcements are facing an uphill battle, however. AT&T released a study last year which found that 49 percent of adults and 43 percent of teens admitted to texting while driving.