Modes Of Transportation Contribution To Pollution: The USA is the third-largest populated country globally, consists of 50 states that have, and are connected, via a vast transportation network system.
The USA transportation system is divided into two categories; highway and non-highway.
This system is mainly used for passenger and freight transport, as shown in Fig. 1. Table 2
shows the number of highway and non-highway transportation in the USA, as well as the number of registered motorcycles (8,666,185) and trucks (13, 233, 910), respectively, in 2018.
This table also shows that the growth of these vehicles has doubled in 1990 when it comes to their contribution in highway transportation.
Other modes of transportation have also shown a considerable increase. Additionally, in non-highway transportation: rail, air, and water traffic numbers have shown a significant overall increase in the last 29 years.
The USA transportation sector is recognized as one of the most intensive systems in their energy consumption.
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Due to the increased numbers in both highway and non-highway transportation, the USA faces detrimental environmental problems that are proving to be hazardous for the eco-system.
Table 3 shows that the highway mode accounted for 82% of USA transportation energy consumption. This essentially means that trucks and cars remain the main contributors to chemical emissions in the air.
However, it must be brought into consideration that the non-highway modes account for the rest of the USA transport energy consumption.
An increase in the number of highway and non-highway modes, and energy usage in the transportation sector is posing a threat to the environment.
It is noteworthy that the transportation sector is responsible for 34% of the CO2 emissions and 28% of all GHG emissions.
Table 4 shows that highway vehicles account for the majority of CO2 emissions, while the air traffic also has a significant contribution to the CO2 emissions in the non-highway mode.
Drivers of CO2 emissions in transportation: A synopsis
In large economies such as the USA and China, carbon emissions from the transportation system remain one of the main components of national emission accounting.
When it comes to the transportation sector, according to various studies, energy consumption, population, and economic growth consistently remain the primary determinants in the possible increase of carbon emissions in the air.
Thus, this peculiar connection paves the way for the attainment of a sustainable and environmentally friendly transportation sector.
Indicatively, to test this phenomenon, Lu et al. (2007) employed the Divisia index approach.
During the period of 1990 – 2002, this task was undertaken in order to investigate the impact of the population intensity, vehicle fuel intensity, and economic growth, among others measures, on carbon emissions from the highway vehicles in Germany, Japan, South Korea, and Taiwan.
The study’s results revealed that rapid economic growth is a crucial determinant of increased CO2 emissions.
Except in the case of Germany in 1993, and Taiwan during the period of 1992 – 1996, the energy conservation performance in the observed countries was found to mitigate CO2 emissions significantly.
However, while Ercan et al. (2016) closely examined the determinants which contribute towards increased carbon emissions in the USA transportation sector, their study essentially revolved around the theory that increasing the use of public transportation in the USA will lead to the mitigation of carbon emissions by a considerable level.
They found that carbon emissions in the USA could be reduced by 766,000 tons annually, and this measurement could elevate to 61.3 million tons annually by 2050, if the public transportation ridership is respectively increased by 9% – 25%.