Even with ALPR retention restrictions, I could trigger a video save and send the police a video of the idiots doing 50mph through the residential neighborhood.
When the reader triggers and takes a picture, it pings your server for a timestamp. It does the processing and records car X at time T provided by the timestamp. You then calculate the speed by the distance between the two meters divided by the time between the two timestamps for X.
Provided that speeding cars are a problem in your neighborhood, I bet you could find the people responsible for the light poles (which likely have power associated to them) to let you install the devices, especially if you're providing the devices and servers.
I don't think you'd necessarily be able to ticket the drivers though, as you're not law enforcement. Maybe you'd be able to work with local law enforcement though.
Maybe I could work with a neighbor, but then things need to be tightly time-synced.
Zero chance I could get light pole access. A city endorsed surveillance system? No way.
I'd maybe like to know if it detects the plates of people I know well nearby (sometimes I wonder when I see a car I feel I recognize), and I'd want to be able to mark bad drivers I see, and be warned if they come near my car again.
My thought is that if I am driving around a driver bad enough that I think about the risk of accident, I might want to know if they're close to me again in the future.