There is an on/off setting for this in Vehicle Setting > Instrument Cluster, but it doesn't seem to do anything on my year old car. So does anyone know what it's supposed to do?

I still have doubts that TSR is working at all in my car. As a supplementary question, is there a difference in behaviour between when TSR sees a speed limit sign as opposed to the change in limit being detected by GPS map data? Scenario would be comparing a clearly visible clean sign to one broken or covered in algae & buried in a hedge.

My car seems to have two ways to detect speed limit signs, either via the map data or via the camera. If it misinterprets a road sign (such as one relating to another road at a junction) then this will override the map data. The camera also fails to see road signs covered by overgrown trees and bushes, or on overhead gantries, or when the sign is not the standard round shape. (I have set the car to only display the current road sign and not change my speed because of these failures... more modern cars may have problems doing this!)

Occasionally the map data is also incorrect, and the speed limit is displayed in km/hour rather than miles/hour! There was one particular stretch of dual carriageway where the car would display an 80 sign rather than the correct 50!

Chris