Hazard Warning Lights & When to Use Them

All cars are fitted with hazard warning lights; you should use them as a warning to other road users. But when should you turn them on?

hazard warning lights
An van showing hazard warning lights illegally parked on the approach to a zebra crossing.

Some drivers use them as an excuse for unsafe and inconsiderate parking. But pulling up on double yellow lines to make a phone call is still against the law; even if your hazard lights are on.

The Highway Code says that you should use hazard lights when your vehicle is temporarily obstructing traffic. But this means an unavoidable obstruction such when you have broken down. You can also use them to warn others when you are parked for loading or unloading. Even in these circumstances however, you must ensure that you do not leave your vehicle in a position which causes danger. You may still be charged with an offence if you are causing a serious problem to traffic flow; or leave your vehicle unattended for more than a few minutes.

Delivery drivers often make the mistake of stopping on yellow lines, partially hidden behind other vehicles. They then switch on their hazard lights unaware that the other vehicles partially block the view of their van. In this situation only one indicator may be visible and it may look as though they are signalling to pull out!

Hazard Warning Lights on the Move

Generally you must not use hazard warning lights on a moving vehicle. The only time you should switch on hazard lights while you are driving along, is to warn others of a hazard ahead on a fast moving road such as a motorway. When you can see traffic ahead which is slowing down because of an incident, you can use your ‘four-way flashers’ to warn drivers further back. Switch them off however once the warning has done its job.

Highway Code rule 116

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