From what I've read, it sounds as if you are not connecting the phone with the car (charger/bluetooth etc).
Thus your best solution (if not getting something additional to connect with the car as proposed already) is steiny180's solution, although I haven't sued the specific software.
Thanks. But how the LOCATION trigger would help to indicate "end of driving"?
You would have a profile variable (say "Car Mode") that changes from "true" to "false".
Using GPS data, perhaps you can estimate your speed in a variable (say "Speed") every 1 minute or so (depends on battery drain etc).
Then you will have a condition:
If "Speed"> 20 km/h (or any preset you want) - Set "Car Mode" to "true"
Else - Set "Car Mode" to "false"
and one more condition
If "Car Mode" is set to "false" - Notify "Switch off your lights".
Thus while you are driving, car mode is true. Once you stop it goes to false and you get a notification.
It is not super accurate, but it would depend on only the speed of your phone.
Something like this will find your "Location" being in the car based on the speed of travelling.
You should have options for traffic etc though, where you slow down but not away.
Another option would be to monitor your phones vibration signals, ie knowing when you walk (higher signal) as opposed to when you drive (lower signal unless you are on the fields
)
These are a couple of ideas to get you thinking