I would like to activate driving mode every time it connects to my car's Bluetooth!

the manual says you can add the car's bluetooth to the location services. I have done this.

but how do I tell the phone that each time it senses me in the car it goes into driving mode?

 

The bue tooth is built into the car!

 

I am not too sure why, but tonight on the way home it went into Drive mode automatically! I am not too sure what I did different!