On the outskirts of Los Angeles, inside a nondescript laboratory building, a man in a yellow T-shirt and helmet sits on a stationary motorcycle, looking intently ahead. The bike's back wheel is spinning, and a long orange tube connects to its exhaust pipe. A fan roars, mimicking wind.
Nearby, on a computer screen, colorful lines show the concentration of pollutants emitted from the motorcycle, such as nitrogen oxides and carbon dioxide.
