Q&A - Using Four Way Flashers

Q&A ImageQuestion: When should you use your vehicle's four way flashers while driving on the highway? I think that some people don't know when to use them and are confusing other drivers. Overuse could cause drivers to ignore them.

Image of finger and four way flashers button


Four way flashers are meant to be used as a warning to other road users that a hazard exists.

The two designated hazards are a vehicle that is disabled on a highway and slow moving vehicles that are either heavy trucks complying with signs or slow moving vehicles.

Rule for Use of Four Way Flashers

This is what the Motor Vehicle Act has to say about the use of four way flashers:

Flashing lamps

4.28 (7) Turn signals, or side-marker lamps used in conjunction with turn signals, may be used as warning lights by a slow moving vehicle as described in Division 7B or as warning lights whenever a vehicle is disabled on a highway.

When Directed by a Sign

The Ministry of Transportation also posts warning signs (not regulatory) on steep grades:


The W-325 SLOW TRUCKS USE 4-WAY FLASHERS ON GRADE warning sign advises commercial vehicle operators and other large vehicles to use their 4-way flashers when traveling downhill to alert other motorists of the speed differential between their vehicle and the other vehicles.

This sign may be used on grades where the operating speed of large trucks is expected to drop 30 km/h or more below the posted speed limit.

It is restricted in use, and should be used on high speed, multi-lane highways or freeways only under the authorization of the Senior Traffic Engineer in consultation with Highway Safety Section. W-326

This sign should be installed at the start of and intermittently along steep and/or long grades.

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