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?
Lenticular cloud, Russia. Captured just at the right moment, when the sun is directly striking the bottom of the cloud and light is refracted through the top of the cloud. It gives an amazing two-tone effect. 'I just learned that this is a hydrogen bomb building a mushroom cloud. Destruction has its short moments of beauty too..'