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?
Japanese photographer Shinichi Maruyama has an interesting series of photos simply titled, “Nude.” Each image shows an abstract flesh-colored shape that’s created by a nude subject dancing in front of the camera. Although the photographs look like long-exposure shots, they’re actually composite images created by combining ten thousand individual photographs of each dancer. The result is a look in which each model’s body is (mostly) lost within the blur of its movement.
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