Rule 116: Hazard warning lights
Hazard warning lights. These may be used when your vehicle is stationary, to warn that it is temporarily obstructing traffic. Never use them as an excuse for dangerous or illegal parking. You MUST NOT use hazard warning lights while driving or being towed unless you are on a motorway or unrestricted dual carriageway and you need to warn drivers behind you of a hazard or obstruction ahead. Only use them for long enough to ensure that your warning has been observed.
Law RVLR reg 27
Why the capitals matter. The Highway Code writes a rule in capitals — MUST or MUST NOT — when it is backed by law, so breaking it is a criminal offence. The rules that do not use capitals are advice.
5 theory test questions on this rule
From the DVSA revision question bank. These are not the questions asked in the real theory test. Each one shows the answer, the explanation, and our own note on why every other option is not it.