Which statement about this safety sign is NOT correct?
A line under the number marks a minimum speed sign; without it, the sign sets a maximum speed (Annex 6 Nos. 224 and 225 of the Enforcement Rule). The minimum speed also has an exception for unavoidable cases such as traffic congestion (Article 17(3) of the Road Traffic Act), so watch for statements that swap the meanings of the two signs.
Answer: ③
Explanation
This sign, with a line under the number, sets the minimum speed for motor vehicles, etc. (Enforcement Rule Annex 6, No. 225). You must not drive slower than that, except when traffic is congested or in other unavoidable cases (Road Traffic Act Article 17, Paragraph 3). 'Do not exceed the speed shown' is the meaning of the maximum speed sign, so that statement is wrong.
Legal basis: 도로교통법 시행규칙 별표6 225 최저속도제한표지