How accurate is the Rolling Road. Calibration and setup, How it works, plus a load of cars revving

In this video I answer some questions about how the rolling road works, how its been calibrated and is so accurate. I also explain the counter intuitive fact that its more accurate at measuring engine or flywheel horsepower than it is at measuring wheel horsepower. I also through in a on of videos of various cars sending it on the dyno.