This. I've frequently been surprised by how useless the audio navigation is without being able to check the screen for clarity.

There just needs to be a "no visuals" setting where you get given much more audio information.

The worst experience I've had was riding in Slavic countries with just headphones in and realising after a few miles that GMaps couldn't pronounce the road names and so was just leaving a silence.

I'd get "Turn left on to ''". I thought the roads were numbered and I was constantly turning onto highway 2.