Good on the people for warning you.
Speeding mobile units are there to help figures, create revenue, meet targets, very rarely are they in a place that would help, more to catch the motorist out.
Surely nobody can say they dont speed, and never go above 30mph.
I agree with Entwi Inappropriate speed is the danger.
I have also follwed enough police cars, not blue lighting, that travel over 30 mph in a 30 zone.
