Post 7651.
Lay assessments of visibility are notoriously wild.
"Visibility" is carefully defined and, inter alia, depends upon recognising an object for what it is known to be.
9 to 10 feet assessments in hill fog are ludicrous and such statements should be inadmissable as evidence.
In 41 years in Met. I don't think I ever saw vis. as bad as 50 metres whilst on duty, and less than 100 metres was very rare.
Worst I ever saw was London before Clean Air Act, and I could believe that was about 20 yards in thick yellow ****e with someone else driving and me half way out the window.