What is a chassis dynamometer and how is it used?

A chassis dynamometer (rolling road) is a laboratory device that allows vehicles to be tested while stationary by measuring power at the wheels against rollers. Uses include emissions testing under controlled conditions, fuel economy measurement, powertrain calibration development, climate chamber testing at temperature extremes, and 4WD system testing. The dyno applies road load simulation based on vehicle parameters and can measure wheel torque and power. Modern dyno cells include emissions benches for regulatory certification testing.