Adding on to what Hakumi said above, it sounds like she may have all of this unused energy built up. Lots of dogs like cars, but if she's chasing them to level that may become dangerous for her, I would try finding another outlet for her to get rid of all that energy. Especially since she's a fairly young dog, it doesn't seem uncommon for her to be rambunctious. Perhaps try giving her long walks during the day and (if you don't already) build a fence around your house so that she can run around whenever she needs to. If you have a dog park near your house, you could also take her around there to give her a change of atmosphere.
As was mentioned above, keeping a leash on her seems like a reasonable precaution at the moment, especially if you're worried about her getting a little too close to those cars. If you let her outside your yard without a leash or fence, it may be a good idea to consider using/investing in those to keep her safe. Teaching her a few simple commands may be another good idea.
If she's stopped being interested in her toys like she used to, she may find enjoyment out of another companion? This is completely up to you and your family and how comfortable you feel about it, but perhaps adding another dog/puppy could bring her attention away from those cars. c: