Because the means of each country to fuel metabolism occurs which is heat and carbon dioxide. Thus, when the amount of traffic it will reduce the number of vehicles burning on the streets each day.
The vehicles, each vehicle will burn fuel, which will generate heat and carbon dioxide. Therefore, reducing the number of vehicles it will reduce the number of burning down the road each day.
Because each one is born vehicle burning of fuel, which can heat and carbon dioxide So when the reduction of the car, it will reduce the number of burning on the road each day.