When first arriving in Australia as a young boy I used to see signs on the roadside stating "Caution: Road Plant Ahead"
I had no idea what it meant as I never spotted any plants causing a problem. I did sometimes see some road works which I guessed where needed as plants had damaged the road.
It was only much later that I learnt that the term plant was used for roadworking machinery.
A childhood belief about road signs

others believed things like this
- I used to beleive that road signs grew out of the ground.— Tiana
- I used to see "End Road Work" signs, and thought they were a sort of protest.— Sebastian
- I used to believe that the sky had stop lights and road signs floating about for the airplanes.
— LoonaSM's - When I was little, I used to believe that deer could only cross the road at the deer crossing signs. — Shellie
- When I was a kid I took two showers becaue I thought my hair was a plant and needed the water to grow— Tim
- When I was a kid, I used to believe a nuclear plant was a clouds plant and could make magic clouds.— Tommy