The author could take a camera on the road and shoot pics for a day or two, then use OpenALPR to predict the plates and check this dataset to see how accurate it is. If it's good enough, it can be used to train a CNN model with real images of cars and no manual labeling.
I started saving file from my dashcam several months ago with that idea - to use the openalpr results as training data for a neural net, but the results I'm getting from openalpr aren't good enough to use without a lot of manual review.
