Resting the camera on the dashboard of the car to keep it relatively stable would be a good approach. Then it's just the car's movement and the cars outside that will create the blur and not camera shake. This will have to be experimental as far as shutter speeds and exposure are concerned. Obviously night time would work best if I am going to record light streaks. The camera pointing at back seat and kids with blur outside?
Lights on the works of Berlin-based artist Stephanie Jung with her beautiful experimental photographs shot during her travels in France and Japan, as well as in and around her city in Germany. The effect created through the multiple exposure hypnotizes the viewer and creates a feeling of being lost in space and time.