There is no typo. In the UK they are commonly refered to as "Number Plates" hence Automatic Number Plate Recognition camera. ALPR tends to be common in North America where thery're referred to as "Licence Plates" which is probably why it's the default nomenclature on this site.

For traffic counters they tend to use inductive pickup loops embedded in the road surface for permanent installations and pneumatic ones consisting of a pair of rubber tubes stretched across the road and connected to a box chained to a nearby lamp post for temporary setups. If they're going to the effort of installing a camera and all the power and data lines as well as image recognition system it might as well be reading number plates as thats just a slight software tweak and effectively makes it a much more powerful tool than just a basic traffic counter.  Also ANPR cameras tend to be placed on main roads at the fringes of larger towns like Norwich to keep a log of all traffic entering and leaving the town as this data can be valuable to law enforcement as demonstrated in the recent "Sycamore Gap" case.

I've mapped hundreds all across the UK because the government refuse to publish their locations and you start to see the patterns in their placement. Some areas have more than others. Other cameras tend to have signs with the details of the operator and data controller but ANPR cameras don't because they're not supposed to be known about. 