Earlier quoted context omitted.
Presumably you could measure the speed at a distance then image the number plate as the car gets closer.
Anything involving fines needs to be absolutely 100% infallible. Taking a speed reading then the plate leaves a lot of loopholes. I don't think any speed operation would work unless the car has been sighted, number plate read and speed detected simultaneously.
I would imagine that a Police officer could testify that he measured the speed using the calibrated device and continued to observe the same vehicle until it was possible to read the number plate.