How can I control this behaviour before it escalates? - Page 1

My 11 month dog is becoming more territorial each day.  He is great when out and about - no aggression to other dogs or people, in fact he loves meeting and greeting.  However, when in the back of my vehicle or behind the fence he sounds like the hound of the baskervilles!!
People have to walk past our boundary fence and he lunges at the fence barking - he is big - they are scared.  If he is out with me on the road - no problem!  He is much worse in the car when I am in it.  I have to sit in a ferry queue and when the man comes to collect the ticket, it is embarrasing! 
Any advice please?

So your German Shepherd doesn't like people walking near his yard or approaching your car? I mean, yeah there are things to be done but it is a German Shepherd, just sayin... You have no issues with him otherwise though right? Nice to people on walks, when they come into your house invited etc?

There is a difference between a warning bark and lunging at the fence with hackles up and teeth bared - I am happy for him to bark at strangers, but the point is that I want him to stop barking when I command him to stop - at the moment, especially in the car he ignores me. He is very headstrong, but it is o.k. - I have had good advice from someone helpful.  Thanks for taking the time to reply.

He is also a young dog, a lot of these drives he is feeling are new, and he is probably going through one of his fear stages. Lucky for you it is a Shepherd and they are not to hard to train. Granted temperament is genetic more than anything else. Do you have any clubs in your area?

Unfortunately no, the nearest is 200 miles so I travel every 2 or 3 months for a couple of days to visit a club.  He is excellent at these events - no problems at all.  He just has a very strong need to protect me and his own territory which I am happy with - I just want him to listen a bit more when the blood gets up.  He never initiates aggression to another dog but if challenged will not back down.  I see your point about his age though - he probably will settle down when he gets a bit older.

give him command to leave it/stop it before he gets to the barking level as soon as he perks up - stop it, and mean it like if he was already barking his head off....get ahead of him in the intensity level. He will probably low bark anyway, or grunt and will put in his "last" word ....one of mine talks back when i correct her, but i don't ease up until she is down and quiet...loud whistle would help too when u loose their focus and they no longer hear you....just saying...LOL..

crate him in the car - train an invisible stop line for the dog to stop in front of your fence (from the inside). Bark / Stop training would help too.

Thanks for the help folks.  He is already responding. :-))

Train another behavior you want him to do and train it until it is so ingrained that he will do it any time anywhere.  Replace the undesirable behavior with this trained behavior. 

I use a few.. Down (lie down), Sit, recall.  I can put my dog in a down any place and that stops the dog from doing XYZ that I don't want the dog to do. 

Most people want a dog to stop a behavior but they do not replace the behavior they want to stop with a behavior they would prefer.  I compare it to biting fingernails... stopping that behavior (which is self rewarding) is difficult in people.  Greater success can be had by replacing biting fingernails with another behavior that is more appropriate. 

Rass - love your "down" technique, replacing the behavior with something else. Will definitely be using that!