In Japan, one character of hiragana is used on every car license plate.
However, only four characters, 「お」,「し」,「ん」 and 「へ」 don’t be used.
Today, I’d like to introduce these reasons.
「お」: Because this character is very similar to 「あ」.
「し」: Because this character implies 「死 (death)」.
「ん」: Because it is difficult to pronounce this character.
「へ」: Because this character implies 「屁 (poot)」, and there is a possibility that interferes your driving by laughing.
Until today, I didn’t know these facts. Hehehe.