Thanks for the links. I am interested in creating my own number plate reader to scratch an itch. How many of those cars on the roads have I seen before?

My hunch is that, on my local journeys, I have seen the majority of cars before, to just see them as generic cars, with none of them special, apart from a few owned by friends and a few idiosyncratic vehicles (tractors, pre-war classic cars and anything else rare).

I could be wrong with most cars being totally new to me, maybe not on the road outside my door, but on the big road that my road joins on to.

My use case is as a cyclist. So that Raspberry Pi will need to be carried somehow. There aren't too many cyclists around in my neck of the woods, therefore, even though I might see all cars as generic boxes, their drivers might see me as 'there is that stupid cyclist again', hopefully to give me space on the road.

We all have to get along on the roads and I don't want any conflict, mostly because I will need to use the same roads again and I wouldn't want to meet someone on the road after some silly road-rage type of incident. Therefore, knowing how many cars are actually new to me would be useful to know.

This applies to so much else, even the birds in the garden, where I can't tell one sparrow from another. It would be great to know which of them are residents and which ones are from out of town. Birds don't wear number plates though.