Do not disturb while driving does not work for texts

I have an iPhone 8 with iOS 11.2.

The do not disturb while driving feature has yet to work properly for me. I do not have Bluetooth in my car, and I have the feature set to automatic. Calls are stopped but text notifications come through. I use Waze on the phone while driving and the constant interruptions are annoying. I thought this feature would be a savior! The manual setting doesn't work either.

What can I do?