Stephen Wallman shows the lambda sond (kneeling behind the exhaust pipe on a Volvo V50)

The world’s perhaps most important invention for controlling exhaust emissions on cars was developed at Volvo Car Corporation in the early 1970s. Under the leadership of the legendary environmental expert Stephen Wallman, the three-way catalytic converter controlled by an oxygen sensor was introduced. Mr. Wallman has now been awarded the Royal Swedish Automobile club’s gold medal.