Hazard warning lights

Hazard warning lights say one thing to other drivers: this vehicle is a hazard. The ordinary use is when you are stopped and temporarily obstructing traffic, or when you have broken down. Using them to justify stopping somewhere you are not allowed to stop is the misuse the test asks about, and it is still an offence with the lights on.

There is one moving exception on a motorway or an unrestricted dual carriageway: if you have to slow down sharply because of a queue or an obstruction ahead, a brief flash of the hazards warns the traffic behind you that something has gone wrong in front. Switch them off once the message has landed.

What they do not do is grant priority, and they do not excuse the thing that made you stop. They also cancel out your indicators while they are on, so you cannot signal a direction with them running.