I heard it every time I was going to drive out of Grandma's driveway. I heard it every time my Dad drove out of Grandma's driveway. Mom was a little less blunt and just admonished us to be quiet so she could hear.
The concern was valid. Grandma's driveway was almost at the bottom of a hill on a state highway. Highway drivers could not see the driveway until they were almost upon it. The driveway and her accompanying four room house were built when the highway was probably nothing but a dirt road and the thought of someone driving by at sixty miles an hour was not even a possibility.
Grandma died in 1994 and my Dad and my brother had to serve as their own sentries when leaving the drive.
My parents moved to my Grandma's farm about ten years after that and replaced the old farmhouse (which didn't have running water) with a new one--and a new driveway at the top of the hill and north of the old one.
The south driveway is still there, but since it's no longer in front of the house it's not used as much as it once was simply because people do drive like bats out of hell on that road.
The first picture in this post is one of my Grandma Neill, taken in the 1980s. I don't even remember why it was taken. You can barely see the highway's yellow "no passing" sign in the background. The infamous driveway is directly behind her.
Sometimes when I'm leaving Mom and Dad's I'll drive out the south driveway just because it's still there. And I'll think Grandma's standing there in spirit, motioning on that the coast is clear.
If Dad saw me do it, he'd probably tell me "be careful they drive like bats out of hell on that highway."