Well, what i wrote was confusing and it was hard to explain.
Sorry i made your head spin...mine did too.
There is more to it. A lot more.
So, when you look down at the instrument cluster of the car...
the tachometer is obviously on the left.
When going a certain speed the tachometer correlates with
the speedometer and rises as the speed does accordingly.
That cop was basically accusing you (he did ask though, smartass)
of watching the tachometer numbers and using it's numbers,
as though it was the speedometer to verify(or keep in check) your speed.
and if so....that would be really fast! If the tach is at number 4
you would be going faster ie...than 40 miles an hour.
Highway driving.
