I can tell you how I do it, not any type of secret.
Plate ABC 123 is identified on a Toyota Prius on Jan 1, confidence score was 85%
Plate ABC 123 is identified on a Toyota Prius on Jan 2, confidence score was 90%
Plate ABC 123 is identified on a Ferrari 360 on Jan 3, confidence score was 50% - you could raise an alert here if you wanted to but odds are good the vehicle is a Toyota.
Plate ABC 123 is identified on a Toyota Prius on Jan 4, confidence score was 89%
You can see a trend here. On my system (using a database of all the plate matches) I have logic that can say that the vehicle associated with ABC 123 is a Toyota Prius. So when OpenALPR (or whatever you are using to identify make/model) says it is a Ferrari, the Ferrari guess is probably wrong.
That is one way I use the data from repeated sightings of a single plate.
Then I also use the same system for SPDV (love that term
@samplenhold ).
Plate ABC 123 is identified on a RAM Pickup on Jan 5, the confidence score is 90% - at this point, I would trigger an alert. The confidence is high and the plate is no longer on a Toyota. In my case, I send an alert for a human review. I capture about 1000 plates a day and using the logic above it might trigger 3 or 4 alerts a day. Most of them are just legit people changing vehicles legally. However, there are people in the area who switch back and forth.
Take this guy for example:
This guy has been switching his plate between these two vehicles for more than 1 year. He actually triggers multiple alarms in my system, both for switching the plate between vehicles and because that format plate should never appear on a pickup truck in our area.
All pickup trucks use a plate format of AA 0000 so putting a passenger plate on a truck tosses up an alarm in my system.
My software is totally custom, so I can't really share it - but the concepts I'm using are not rocket science. The user
@mlapaglia is doing some amazing work on his OpenALPR add-on, perhaps he can add some of these features. I tried sending him a couple DM's but he has not replied.