It means that you are in prison and dreaming of freedom.
Actually, it could mean many things ... or nothing at all.
Your dream suggests that you have a void or empty space in your life.
Empty dreams mean that you do not experience any dream. You feel empty while sleeping. It is like a blank paper at night.
If by this you mean only "hot heat" when drive at highway speeds likely thermostat bad and/or almost stuck and takes long time warm up from high engine RPM during highway driving.
If you mean Book... Then it is inadvisable to read while driving, under any circumstances.
means you are going to be a bad driver
It means that you are having a random dream.
The dream is recurring because you have been feeling lost and without any specific direction in your life for some time now. The highway symbolizes your life. This dream is likely to recur until you find a purpose that is worthy of your full effort and commitment.
To dream someone is driving backwards means that the dreamer is dependent on the driver and that the person driving is leading the dreamer the wrong way. If the dreamer is driving backwards it means that the dreamer's life is going in a direction in life they know to be wrong.
This dream expresses the dreamer's feeling out of control in real life. The dream illustrates feared consequences of being out of control of events.
The dream is merely an acknowledgment of the partner's absence and an empty space in the dreamer's life. The "someone else" represent's the subconscious mind's effort to fill the empty space, much as the zero fills a space in mathematics. There is no sense of unfaithfulness in the dream.
This dream seems to express the dreamer's grief, facing a vast, empty (?) future without the companionship of the lost friend.
No passing when driving in that direction while it is solid.