Can I suggest that if you are concerned and if you know your neghbour, even if it is just to nod at, that you go and speak to him first and see what is going on - there could be many reasons why the dog is kept in the car, from your post it doesn't appear that you have spoken to him about it - I maybe wrong.

Think about how you would prefer that this is dealt with if the situation was reversed, after all how many people on here have gotten upset that someone who didn't know their circumstances wrote a note, reported them etc etc

__________________
Love your dogs

http://www.tollpeppertollers.co.uk