With this sign, your travel will become slower (5,5)

I believe the answer is:

speed limit

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But I can't explain it at all! Could you help me understand?

(Other definitions for speed limit that I've seen before include "Rule facing drivers" , "Any faster might generate a fine" , "prescribed for the fast" , "maximum rate by law" , "permitted maximum velocity?" .)

I've seen this clue in The Hindu.

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