I have walked our dog down our long driveway for the past week. Now she will no longer walk to the end. Any suggestions?

Thank you so much for all that you do. I have learned a lot from your web site and videos while preparing for and working with our new Aussie puppy (8 weeks old). We have had her for 1 1/2 weeks and she has been doing well. She is submissive in the crate, housetraining is going very well, and we have started a little obedience work. Here's my question: The dog seems to be about midway (maybe a little soft) on the scale of soft to hard. We live in a suburban neighborhood on a 2 acre corner lot. I had developed a routine of walking her (always on leash) down our long driveway and then along the curb/street edge surrounding our yard. The walk has hills but she never seemed to become overly tired during the exercise. Cars and/or construction vehicles drive along the road occasionally but it is not a busy road in the least. All of a sudden, with no precipitating incident that I can recall at all, she will no longer walk to the end of the driveway. She literally lays down and drags her claws if I try to take her to the end of the driveway for our walk. She shakes and pulls backward. She seems to be terrified of the road. I have tried to jerk the collar with varying levels of force and she still resists. I have reversed the direction of our routine and she seems to fear the road from other starting points as well. Her bathroom spot is near our house so she hasn't had potty issues as a result, but it is very difficult to exercise her when she won't walk more than 50 feet down our driveway. I have tried picking her up and carrying her out to the road but she still resists all along our route. I'm guessing that the cars/trucks on the road must scare her but that will not change and I can't alter our walking path b/c I don't want to venture too far from our home (small children at home). I would really appreciate any suggestions you may have. She otherwise is, so far, an obedient, willing to please dog.

Thank you,
Ashley