Senecio:

 

I think you misread the post. He's saying that when his car's speedo is indicating 100km/h, he's only actually travelling at 96km/h

 

Ah good point. Figured that over reading was fairly common, so I don't see how a radar really helps in that regard. I mean if it says you're doing 105kmh on your speedo then that's your margin of error. I mean phones give you that data now, so do plenty of those Your Speed Signs. 

That said I think we all know why people buy radars, I haven't really kept up with it. An old boss who had every supercar under the sun would change radars every few years. I presume in response to different detection requirements and most often false alarms.