Bad manners where driving is fastest? (8)

I believe the answer is:

highways

'where driving is fastest?' is the definition.

'bad manners' is the wordplay.
'bad' becomes 'high' (both can describe rotten or decayed food).
'manners' becomes 'ways' (I've seen this before).
'high'+'ways'='HIGHWAYS'

(Other definitions for highways that I've seen before include "Public roads" , "Main roads" .)

I've seen this clue in The Telegraph.

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