How to set the google maps app foremost while driving
Use Android Auto.
This will reduce the accessing time for Maps or Any other application required while driving. Also During driving and using android auto, you'll have a better experience of Map as the notifications from other apps won't bother you as they do on running the Maps app directly.
Reason for this is to minimize the interruption of other apps while driving.
Android auto is designed with keeping these points in mind and to make driving safer.