No matter what kind of fuel is used by the vehicles, using public transit can reduce air pollution. Because public transportation can carry a far higher number of people than private automobiles, which can only transport a much smaller number of people, there are fewer hazardous substances in the air for each person who chooses to walk, ride a train, or take a bus.
Many people believe that since it is less effort, using own vehicles is preferable to using public transportation. This would result in a significant increase in the number of vehicles on the road, which would increase emissions of fuel residue like smoke, which contains air pollutants.