Recently, Rosie barks and tries to lunge at cars driving by when we go on our walks. 
It only happens on our street as we go to the park (i.e. when the car drives *right* by) - once we are in the park, we walk on a path through the woods, then for a little while, another path alongside a parkway. That separation of maybe 20 feet or so from the parkway is sufficient such that she ignores the cars going by and the barking/lunging is not a problem.
When she does bark/lunge, it is potentially very dangerous. I hold her leash very tightly so that she can't get anywhere near the car. I worry, though, that one of these days my grip will slip, or that she'll do it when one of the kids is walking her. She only weighs 14 lbs, but still.
She gets 3+ walks per day, so the potential for something bad happening is high enough that it worries me.
How can I break her of this bad habit?
It only happens on our street as we go to the park (i.e. when the car drives *right* by) - once we are in the park, we walk on a path through the woods, then for a little while, another path alongside a parkway. That separation of maybe 20 feet or so from the parkway is sufficient such that she ignores the cars going by and the barking/lunging is not a problem.
When she does bark/lunge, it is potentially very dangerous. I hold her leash very tightly so that she can't get anywhere near the car. I worry, though, that one of these days my grip will slip, or that she'll do it when one of the kids is walking her. She only weighs 14 lbs, but still.
She gets 3+ walks per day, so the potential for something bad happening is high enough that it worries me.
How can I break her of this bad habit?