I took this pic before the previously posted one, If the car were to travel the same speed the entire time the shutter was open it would simply be a green unidentifiable streak across the picture. I had wanted to actually show that car, so I had to have it sit still for part of the duration. In the pic I opened the shutter waited one second and then pulled the car forward by tugging on the piece of construction paper. The picture, as you can see, appeared with the streak in front of the car. I wanted them coming from the back. So I tried a few more times, pulling the car backwards. So, woody, you were right, the car IS going backwards in the other pic. I wanted the car to look like it was driving by and decided that if it was going forward the front would be semi-transparent because you can, in fact, see what was there before the car got there. I hope all this makes sense. I suppose this picture could represent a car accelerating, but either way the car must be idle at some point to appear at all thanks for the comments