To summarize my experience:
1. I have turned Siri on and thus bypass the voice control from taking charge
2. I have disabled Siri from being activated from the lock screen
This all should prevent accidental activation of the voice related communication with my phone, but it does not.
This is what I see happening:
When I start my car (Peugeot 3008) with my iPhone 6 (iOS 10.1) in my left front pocket I can see a dummy call initiated on the car radio and hear the radio program being muted. The only way to resume listening to the radio is to make a phone call from the handset. The connection between the handset and car radio is bluetooth, not Carplay.
I did a test with the car running and radio playing. When the phone is inactive touching the home button does indeed acticate Siri to ask how she/it can assist me, giving a list of cases how to assist. At the same time the car radio is muted and a dummy call is initiated on it. Pressing the power off button on the side of the phone turns Siri off and the radio on again.
If there is a way to eliminate Siri before the phone is properly opened then that would satisfy my needs. Simply disabling Siri doesn't do the trick.
The ultimate request from me would be to be able to toggle both Voice control and Siri off and simply use the phone with my fingers. But this will require actions by Apple in a future version of iOS.
Meanwhile, Siri has a parameter "Voice feedback" which I have turned to "Control with Ring Switch". All options have voice feedback on when used with bluetooth.
There is also a "Restrictions" section under General parameters in settings, that I now will try out. I can see that you can turn on restrictions and deny Siri & Dictation as well as CarPlay. I'll give this a try and inform you dear followers if this has any impact for me.