The Volkswagen diesel emissions scandal of 20J 5 not only pushed that
company's stock and retail sales into freefall, but also raised serious questions about the efficacy of existing regulatory controls. The same furtive actions taken by Volkswagen had been taken nearly twenty years earlier by other firms in the diesel industry. In that previous scandal, the U.S. Environmental Protection Agency (EPA) discovered that diesel truck engine manufacturers had, like Volkswagen would later do, programmed on-board computers to calibrate their engines one way to satisfy the required emissions test but then to re-calibrate automatically to achieve better fuel economy and responsiveness when the trucks were on the road, even though doing so increased emissions
above the mandated level.
Cary Coglianese & Jennifer Nash,
The Law of the Test: Performance-Based Regulation and Diesel Emissions Control,
Yale J. on Reg.
Available at: https://digitalcommons.law.yale.edu/yjreg/vol34/iss1/2