What it really means

I used to think this meant "Be cautious, drive carefully, there is precious cargo on board." I used to think it was a warning to other drivers.

I still think it is a warning to other drivers - to be aware that the driver of this car has not slept through the night in 6 months, does not have both hands on the wheel because her right arm is twisted up and behind her to grab Sophie who fell overboard and has the pedal to the medal because she figured she had enough time to get home before needing to nurse but she underestimated Bay Bridge traffic and now she has a screaming infant in the back seat who doesn't give a *@#% about the Itsy Bitsy Spider.