Cars are already indispensable in our daily lives. Automakers analyze the components of exhaust gas to ensure engine efficiency, and to make sure they do not pollute the atmosphere.

At maintenance factories or gas stations, a car is not in motion although its engine is on (this state being called "idling") when the exhaust gasses are collected from its tail pipe for inspection. Automakers use a more sophisticated method. They collect exhaust gasses from the tailpipes of running vehicles. Isn't it difficult to make an analyzer and connecting tubes run together with the car?

There is a tool known as a chassis dynamometer that is used in this particular situation. Even though it is called a "meter," there is no scale on it. The instrument employs an electrically controlled metal roller, just like a treadmill. There are a variety of car running patterns regulated by law, such as a "town driving" pattern or an "expressway driving" pattern. You might recall the "10 modes" sometimes found in car catalogues.

The chassis dynamometer controls the roller electrically following these patterns, and re-creates the actual situation of a car traveling on real streets. There are also many other patterns in different places around the world. In this way, automakers are always studying more capable and fuel-efficient cars.