Dieselgate: Clean in the Lab, 40 Times Dirtier on the Road
Bottom line: Volkswagen did not just make a dirty diesel car. It built software that knew when the car was being tested — and behaved clean only then. On the road, the same cars emitted up to 40 times the legal limit of nitrogen oxides. What finally caught them was not a regulator, but a small road test run on a $50,000 research grant. What was the "defeat device"? A defeat device is software that changes a car's behavior when it detects an emissions test. Volkswagen's version watched the steering wheel, the wheels, and the driving pattern. If the wheels were turning but the steering wheel was not — a sign the car was on a test rig — the software switched to a clean, low-emission mode. In normal driving, it switched back to a mode that gave better performance and fuel economy, but released far more nitrogen oxides (NOx) than the law allowed. NOx is not just a number on a chart. It irritates lungs, worsens asthma, and contributes to smog. Diesel engines are efficie...