Your problem is a lot easier because the problem is very restrictive. You don't really need the program to read the plate in general, since it will only need to recognize the exact same plate(s) of the car(s).
You only need to identify and segment the part of the image corresponding to the plate. After applied the appropriate affine transform (rotate, scale) and color adjustment, you can simply use template matching of the read-in car plate with the previouly stored image.
Try