When analyzing a car dream, it is important to ask yourself the following questions about the context of the dream:
Where are you? If you are sitting- which seat are you in? Sitting in the driver's seat shows you that are in the driver's seat in your life- you have control or attempt to. If someone else is in the driver's seat, it is possible this person or what they symbolize to you is controlling your life. Sitting in the passenger seat may mean you have a passive approach to life. Sitting in the backseat may mean you are taking a "backseat" in your life or specific situations. It is important to keep in mind that other people often do not symbolize themselves but rather an aspect within you that you identify with them (example, your angry aunt may symbolize your anger or your negative approach to something).
How's the ride? How the car is riding often shows us how many obstacles and hardships we are experiencing. A bumpy ride, seeing rocks in the road or see other obstacles and dangers including traffic signs indicating danger show us what environment we are currently navigating through and how easy or hard we feel it has been to get through.
How do you feel in the dream? Driving fast and experiencing a sensation of elation means something quite different then driving fast and experiencing a feelings of fear and panic.