Here’s the thing. You’re driving using Siri as a Satnav on your iPhone. Since the phone is plugged into the car and therefore thinks it’s on mains, you can just say “Hey Siri” and ask it what you like, when you like. It is great.
You’re navigating along and you get a text. “Hey Siri, read my texts”, you say. And it does. That’s nice.
What’s a lot less nice is that your iPhone then sits on that grey-black Siri page waiting for you to press the button to ask it something else.
Don’t. Do this instead. Say: “Hey, Siri, what’s our ETA?”
Siri will tell you. Many people don’t realise you can do this at all but the trick is not that you can do it but that Siri reacts in a certain way. It tells you the ETA – and then it goes back to navigating. It goes back to the map and its turn by turn directions instead of the grey-black emptiness of the Siri page.
There will be other questions that work but the ETA one seems to do the job because it is related to navigating. Somehow iOS 8 knows to pop you back to navigating after you’ve asked this.
Bonus: when you do this a lot, as I do, you get to ask the ETA many times and you get to learn what your ETA is. I rarely care but now I’m very familiar with distances on the motorway.