How do I turn off driving warnings? Since I updated to iOS 11 it's been warning me about using the phone while driving. I'm not driving. I'm on public transportation. How do I turn off the warning?
This is how it's designed - you need to override it each time the device detects a potential driving situation.

You need to turn the feature off manually one by one or once systematically to disable the checks and warnings.

How to disable automatic Do Not Disturb While Driving

By default in iOS 11, the feature is set to switch on automatically in the background. If you're almost always the driver, and rarely a passenger, you can leave it like this.

When it activates you get a permanent notification show up on your lock screen indicating that it is doing its thing. If you're driving, leave it alone. If you're a passenger, you can long-press on the lock screen notification and choose to deactivate it. 

If you're almost always the passenger and rarely the driver, you can stop it coming on automatically by heading to Settings > Do Not Disturb then scroll to the bottom of the screen and tap on the "Activate" option. Here you can choose the "Manually" option so that it never comes on by itself. 

Once you have chosen the manual activation, you can add a control to Control Centre by going to Settings > Control Centre > Customise Control Centre and adding the Do Not Disturb While Driving control. Now you just need to swipe up to reveal Control Centre and tap the little car icon to activate it. 

From: http://www.pocket-lint.com/news/142217-how-to-disable-or-customise-do-not-disturb-while-driving-in-ios-11