The article discusses how using public transport like buses and trains can help reduce the amount of harmful gases in the air. Researchers studied the New York City transit system to see how much pollution it creates and how much it prevents. They found that for each unit of pollution the system makes, it helps the area avoid more than 8 times that amount. The study estimated that the transit agency in New York prevents about 20 million metric tons of pollution yearly. If each ton of pollution costs $30 to offset (as projected in a climate bill), the city's transit system could be saving around$600 million dollars annually by reducing pollution. This shows the financial and environmental benefits of investing in public transportation systems like buses and trains.