As a little un my Mum had an old VW beatle and I used to think that the speed limit existed because if you went over the speed limit, all the buildings would collapse because of the increased vibrations of the car! That's why you were allowed to drive really fast on the motorway because there were no buildings!
A childhood belief about cars

others believed things like this
- I always had to sleep with my feet under the covers or else speed racer would drive over them.Anon
- I used to believe that there was a time limit whilst using the loo.— Helen
- I used to believe there was a limit on the numbers you could count — Carmen
- i used to believe that scaffolding was used to support buildings when they were having work on them.Anon
- I used to think 'To Let' on disused office buildings meant they were big toilets.— Tracey
- I once thought people would keep growing until they were as big as buildings if they didn't go to the doctor. — Tufty