New Dog Terrified of Cars While on Walks

We just brought home our 8 month old German Shepard Maggie from a rescue. Maggie was a stray when the shelter found her near St Louis. Now, she is a resident in northern Wisconsin. She is one of the sweetest dogs i have ever met. Within 5 mins of having her, she was playing fetch with my 5 year old son; being extremely patient and gently with him. Maggie is not vocal, have only heard her bark twice, shes house broke, is not a chewer (unless its her toys) and when its time to sit and relax shes as cool and mellow as can be. Maggie gets very excited for meals and eats quickly. I have been able to get her to sit and stay until i am finished filling her bowl before she starts gabbling. Working with her for only a few days, she quickly learned and responds to her name, sits on command and has stopped jumping. Very smart girl. She was also doing great on a leash. Our first time out, she was a heavy puller. After working on a few leash exercises, she walks right along side me, follows does not lead and sits every time we come to a stop. The girl is a dream come true. Que the car...

I live in a fairly quiet neighborhood on a dead end street (last house on the block). This means no passing cars. Our first couple of walks were great. a few bad habits were quickly corrected and she was very calm while walking. Being February in Northern Wisconsin, the sun doesnt come up until around 7am and its dark by 6pm. I work early and having active kids, we dont settle down for the day until 7pm (if we're lucky). This means morning and evening walks are in the dark. Up until now, she has seen and heard passing cars in the distance. Headlights and all. Maggies ears always perks up and she would become hyper aware of that vehicle. But never anything more then that. Last night, my neighbor, in a pick up truck, drove by us as we were walking and she quickly moved away and never allowed her back to the truck. Once it was past, she continued walking, turning her head back to look at the truck as it was now parked. No more then a minute later, a car turns onto our street ahead of us a full block away and she was done. Maggie booked it the opposite direction and pulled like it was the Iditarod. We headed home and she seemed fine once back in the house.

The next morning (this morning), Maggie and i headed out for our morning walk. I purposely stayed home a little later then normal, waiting for the sun to peak up for some light while walking. Once we had some light, we headed out. We only got 3 houses down the block when a car pulled onto our street a full 2 blocks ahead of us. Again, she turned and ran. This time i brought treats that she really likes, thinking i could distract her fear with those. Putting one right in front of her nose, she didnt even notice it. Walk over.

Driving in my truck sitting next to me, she does great and doesnt bat an eye lash at passing vehicles. its only when walking that she is terrified of vehicles. Even ones that arent passing or very loud.

What do you all think i could do to help?

Thanks!