They have difficulty walking or moving.

他们行动困难。

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The DfT guidelines state medical conditions such as autism do not qualify someone for a badge unless "they are unable to walk or have very considerable difficulty in walking".

BBC: Berkshire autistic boy's mum refused blue badge

Old folks sometimes have difficulty seeing, much less holding a pencil and writing, let alone walking to the mailbox or the post office itself.

FORBES: After The Post Office