In all of my...mumble...mumble..."many" years of driving, I had never actually seen the state regulators in action at a gas pump.
The Department of Transportation in each state tests the calibration of gas pumps to make sure they are accurate. I think regulators check both the measurement of the gallons and the octane, and I always wondered how that was done and why I had never run into anyone doing it.
This morning I ran into these regulators at West Nashville Costco. The testing truck was pretty snazzy.