Given the following reasoning and answer, what was the question? The relevant information is: They were first introduced in the UK by section 51 of the Road Traffic Act 1960 (repealed in 1972 and replaced by later legislation).
The answer: 1960
The question Passage: Double yellow lines mean no waiting at any time, unless there are signs that specifically indicate seasonal restrictions. They were first introduced in the UK by section 51 of the Road Traffic Act 1960 (repealed in 1972 and replaced by later legislation).

Question: Based on this passage, when were yellow lines introduced in the uk?