This seems to be a command, along with consequences for not obeying the command.
Several of these signs are located on U.S. Highway 55, in south St. Louis, Missouri. While I’m making fun of the wording of this sign, I’m not trying to make light of the injuries suffered by highway construction workers. According to this site,
More than 1,000 people are killed and 40,000 injured (including drivers) in US highway work zones each year, according to the Federal Highway Administration. Work zone fatalities have increased 50 percent between 1997 and 2004.
