When I was very little I used to believe that the big yellow-colored machinery vehicles (bulldozers, back-hoes, etc) were so big that they took up both lanes in the road (all 4 if we were on a big highway) and all the cars that wanted to go through would have to drive under them. I was terrified of this because I thought that they were so low to the ground that if your car was too tall it would get crushed. This also explained why the traffic got slower near construction sites: because the other people were terrified of getting crushed by driving under the machines, so they would be forced to just follow behind these machines which I thought could only go up to about 5 miles per hour.
You can imagine my relief when there was one on the road ahead of us and we just drove past it in the other lane.
A childhood belief about cars

others believed things like this
- I believed that the gap between the double yellow lines in the road was a special lane for motorcycles.— Joel
- I used to believe fax machines instantly teleported a piece of paper to who ever you wanted. Anon
- I thought you were supposed to drive down the center of the road.— Cassiopeia
- I used to believe, driving in front of all the other cars on the highway, Knight Rider was leading the pack.— Michael Kolassa
- i believed that little men sat in the back of vending machines and pushed the sweets forward.— rachael
- I used to believe that self drive cars actually drove themselves!Anon