Then they have already subtracted their margin of error, which is definitely above 2km/h.

More likely they saw e.g 66km/h in a speed gun with 4km/h error, so they know you did at least 62, and can book you stating 62. But most likely you were doing 66 or even 70 then.

In NZ, which generally copy-pastes VIC's traffic laws, the tolerance is only applied to automated systems like speed cameras. A cop can ticket you in-person when you're 1km/h over.

Are you sure? I got a ticket in Victoria 2 years ago from an standalone camera and it explicitly included a few % grace. The sample image includes it too: https://online.fines.vic.gov.au/Assets/Images/refNo-mail.jpg

> "The alleged speed is lower than the detected speed to allow for tolerance in detection equipment"

The fines are at least a bit more reasonable there. Do you find them reasonable or are they different for locals?

It's almost as if the speed limit is the speed limit!