Slow down for safety?

I walk down Holly Street in San Carlos every day when leaving work. These signs went up just this past week and are on every lawn.



As I mention in the comments, I don't think it's a matter of safety for kids in the neighborhood. I think the residents of this street are fed up with not being able to back up out of their driveways when traffic is coming through. My solution is to have them back up into their driveways when they come home. I'm surprised that no one does that.