The car is very often representative of our own personal space, an extension of our being. It also stands for spiritual direction and motivation.
Psychological / Emotional Perspective:
Dream scenarios involving cars are often much to do with what we are doing to ourselves on a psychological or emotional level. Being alone in a vehicle indicates independence, while dreaming of the brakes shows our ability to be in control. The car engine indicates the essential drives with which we have to deal. A crashing vehicle suggests fear of failure in life, while a car on fire denotes stress of some sort, either physically or emotionally. To be in a car which is driven carelessly, either by us or someone else, marks a lack of responsibility, while a feeling of being left behind would be shown by your car being overtaken. To dream of reversing a car registers a feeling that we are slipping backwards into old patterns of behaviour or are having to reverse a decision.
Everyday Material Aspects:
To dream of being in a car usually alerts us to our own motivation, thus driving the car can indicate our need to achieve a goal, while being a passenger could indicate that we have handed over responsibility for our lives to someone else.
You may find it helpful to read the entries for Journey and Transport.