The car symbolizes the state of progress and the road ahead is muddy. You just need to think about the literary metaphor of this sentence, which means that the road ahead of you is not easy. Only you are left in the car, which symbolizes that you feel lonely. No one can help you, even your boyfriend just walks with you to the car, not with you.
As for what kind of road this road is, the dream also gives obvious hints-it is the workplace.