Australian transportation emissions

The transport sector, as the main user of petroleum fuels, contributes to the production of greenhouse gases, mainly carbon dioxide. The Department of Climate Change defines the sector as encompassing road, rail and domestic air and water transport. Road transport comprises passenger vehicles, light commercial vehicles, trucks, buses and motorcycles. Domestic air transport comprises commercial passenger and light aircraft on domestic routes using either aviation gasoline or jet kerosene (international air transport is reported but not included in Australia's total emissions in line with international guidelines). Coastal shipping consists of domestic shipping and small craft (international shipping is reported but not included in Australia's total emissions in line with international guidelines). Rail transport includes diesel freight trains. However, electric rail is included under electricity generation. Hence, under this measure, the public rail transport network in Sydney, which is electrified, has zero transport emissions.

Contrary to popular perceptions, the transport sector contributes relatively little to greenhouse emissions. The Department estimated that in 2007, transport contributed 14.6 per cent of Australia's emissions (up from 13.7 per cent in 2006). Road transport was the main source of transport emissions in 2007. Passenger cars were the largest contributors to transport emissions. Other forms of transport are much smaller contributors.

Australia's transport CO2-e emissions 2007
	Emissions (Mt CO2-e)	Per cent of total
Civil aviation	5.3	6.7
Road transportation	68.5	86.9
Railways	1.9	2.4
Navigation (domestic)	2.9	3.7
Other transportation	0.0	0.0
Total	78.8	100.0

Source: Department of Climate Change, National greenhouse gas inventory, 2007, p. 20

In 2003, the Bureau of Transport and Regional Economics published projections of carbon dioxide equivalent emissions from transport in Australia. The study, titled Greenhouse gas emissions from Australian transport—base case projections to 2020, contained three scenarios—a base case, a high or 'pessimistic' scenario, and a low or 'optimistic' scenario. The base case projections were a 58 per cent increase in carbon dioxide equivalent emissions from 1990 levels by 2010, and a 78 per cent increase by 2020. The optimistic scenario projects a 49 per cent increase by 2020, while the pessimistic scenario projects a 109 per cent increase by 2020.

Caution should be used when using these projections because the assumptions on which they are based may or may not prove correct, and outcomes can differ substantially from projections.

Department of Climate Change, National inventory by economic sector 2007, Australian National Greenhouse Accounts, Australian Government, May 2009.

Department of Climate Change, National greenhouse gas inventory: accounting for the KYOTO target, Australian National Greenhouse Accounts, Australian Government, May 2009.