Nitrogen oxides (NOx) are the primary source of air pollution from transportation, primarily emitted by diesel engines.

Sulfur dioxide (SO2) is not a greenhouse gas emitted by transportation. It is primarily emitted by industrial activities.

Emission control refers to the reduction of vehicle emissions through technological improvements, such as catalytic converters and particulate filters.

Idling the engine for extended periods is not a fuel-efficient driving technique. It wastes fuel and increases emissions.

Fuel substitution refers to the use of alternative fuels, such as electricity, hydrogen, and biofuels, in transportation.

Using public transportation typically results in lower transportation costs compared to using personal vehicles.

Transit-oriented development refers to the practice of designing cities and towns in a way that encourages walking, cycling, and public transportation.

Vehicle scrapping is not a pollution prevention strategy in transportation. It involves the disposal of old vehicles, which may result in environmental pollution if not done properly.

Waste prevention refers to the process of reducing the amount of waste generated by transportation activities, such as reducing packaging and using reusable materials.

Light pollution is not typically associated with transportation activities.

Transportation demand management refers to the practice of using vehicles and transportation systems in a more efficient and sustainable manner.

Congestion pricing is not typically considered a transportation demand management strategy.

Intelligent transportation systems refer to the practice of using technology to improve the efficiency and sustainability of transportation systems.

Electronic toll collection systems are not typically considered a type of intelligent transportation system technology.

Transportation policy refers to the practice of reducing the environmental impact of transportation activities through policy and regulatory measures.