For users who rely on the Apple Maps app for in-car navigation, Apple snuck a handy feature into iOS 7.1.
While getting voice navigation prompts has never been a problem if you’re already listening to music from your iPhone, users who prefer to listen to the radio or some other audio source normally had a problem hearing audio prompts through their in-car system.

If you’re running iOS 7.1 or later, however, and have a supported in-car audio system, the Apple Maps app can now send voice navigation instructions through the Hands Free Profile, basically sending audio through the same channel that would be used for an incoming phone call, rather than Bluetooth stereo.
To enable this, simply tap the audio icon in the bottom left corner of the Maps app while navigation is active, and toggle on “Allow HFP Prompts.” Once enabled — and provided your vehicle supports it — you should hear voice navigation instructions regardless of what audio source you’re listening to, and in some cases even if your stereo is turned completely off.
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