Subaru Legacy BN/BS (2015-2019) Owners Manual: If you park your vehicle in an emergency

The hazard warning flasher should be used in day or night to warn other drivers when you have to park your vehicle under emergency conditions.

Avoid stopping on the road. It is best to safely pull off the road if a problem occurs.

The hazard warning flasher can be activated regardless of the ignition switch position.

Turn on the hazard warning by pressing the hazard warning flasher switch. Turn it off by pressing the switch again.

NOTE When the hazard warning flasher is on, the turn signals do not work.