You also need to bear in mind a couple of things:
Firstly each Police force will have its own system for ANPR, so the process for making a check in London may well be slightly different from say Devon.
In saying that, they all check against the same basic databases so the results should be the same. I say should, and will explain why so.
When a vehicle passes an ANPR camera/vehicle, the system will NOT send every reg number off to be checked - the volumes of data traffic generated would be simply massive. So, most of them will have a copy of the database working locally - with the ability for the odd "live" check to be done on an exception basis for clarification etc.
Some forces will upload the data daily, others less so. As you can imagine this is a lot of data - athough will fit on a memory stick and can be plugged into the vehicle based system.
There will also be local tweaks, such as a specific local copy of any uninsured vehicles that are SORN etc.
So, although the source data is from the same place, the age of the data will differ slightly and give some variance. As has already been said, a degree of leeway is there - but basically dont risk it.
I'm all for ANPR when used in this way. What I'm dreading is them linking up the systems and using it to provide a national average speed camera network. The concept is exactly the same as the average speed check cameras.
Think about that one
