Save Battery by turning off the display when not in use.
Currently when I use waze, my phones display is draining the battery. I have the following suggestion to reduce the battery usage. If you could include this in future release, I am sure everyone will turn on waze even if they don't need navigation assist.
My suggestion
Turn off the display automatically after a certain speed or give the user an option to turn off the display without locking the phone. This will be very helpful to reduce battery usage when you travel familiar routes and long road trips.
Turn on the display automatically when there is a voice command and when the vehicle is below certain speed. (that's when users look at the display) and have an option to turn on the display by waving hand in front of the camera.

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Vit commented
when driving on the highway, long minutes is not needed to watch waze, might be good to put it into some sleep battery saving mode, (only if battery would really be saved significantly)
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Steve Peterman commented
or at least the option to dim after a selected time interval, and to return to brightness level as described above. great suggestion KurianJ. :)