I knew a dog that barked in the car. After one trip of treats he stopped barking, and he got it. Eventually, a quiet car ride would mean one treat. Try it. I used goldfish (crackers, not real fish!).....

Dogs will do just about anything for a treat!

Let me know if it works.....!

Just say "NO barks"....and when he stops, say "Good doggie"...and give him a treat..... then do it the next time, assuming he will be right by your side or nearby when it happens. So you will be rewarding good behavior and discouraging bad behavior. When you find yourself in a situation wwhen you think he would normally bark, say the No barks thing, then good doggie, then give him a treat for NOT barking....

Good luck.