It's read as "Slow, children at play." In expanded form (plain English): "Please drive slow, there are children here." Naturally, reckless drivers in residential areas have caused the death of several children in the past due to the fact that cars are on average 2,600lbs of self-propelled metal that can drive faster than a cheetah can run and hit a little harder than a bullet and a little softer than a freight train. The fact that we need this sort of reminder is proof that we live in a point on this timeline in which some people can't comprehend the fact that driving like a maniac around micro-humans still under going their 18-year-long period of firmware updates will result in the death of some of those micro-humans.