Myth: Cars aren’t the biggest greenhouse polluters, so there’s no point focussing on them

Fact: True, the majority of greenhouse emissions come from sources other than cars and trucks. But the proportion of emissions from most other sources is declining, while that from cars and trucks is spiralling out of control. And getting big reductions in electricity consumption or agriculture (for example) involves much greater hardship than getting big reductions in car and truck use through sustainable transport and land-use planning.

Shifting from (petrol or diesel driven) private motor vehicles to walking, cycling and public transport reduces the amount of carbon dioxide we pump into the atmosphere, and so mitigates the threat of long-term climate change, which if unchecked is likely to destroy the Great Barrier Reef and reduce the food-growing potential of the Australian continent.

Although public transport still consumes energy, it consumes much less energy per passenger than car transport—even electric car transport. Currently, nearly 95 per cent of Australia’s transport-related emissions come from cars, trucks and planes; less than 5 per cent comes from trains, trams and buses. (Shipping and off-road transport accounts for another small portion.) A 2008 study found that Melbourne’s total greenhouse emissions from transport—some 11 million tonnes of CO2—are 30% higher than London’s, despite London having twice the population.

However fast or slow Australia’s transition to renewable electricity proves to be (and keeping in mind that Melbourne’s trams already run on 100% renewable energy), increasing use of public transport will add much less to emissions than equivalent reductions in car use will subtract from them. Even by shifting a fairly modest one in five car trips to public transport, we can reduce car emissions by 20%—and in so doing also reduce by 20% the magnitude of the task of transitioning to electric vehicles. We can do this without significantly increasing overall transport emissions—particularly if the focus is on the vast majority of journeys that take place outside peak hour, or in suburbs that have little or no public transport at present.

But of course transport is far from being the only source of our greenhouse emissions. It accounts for a little over one-sixth of our emissions, whereas electricity generation accounts for nearly one-third (albeit slowly declining). Sometimes this is taken to imply that emissions from transport are being unfairly singled out for undue attention. First get electricity’s share down to one-sixth, people say, then we can worry about transport’s share.

The road lobby is especially fond of this argument, since it serves their interests. Transport emissions can be further downplayed by artificially separating out the different components (such as cars versus trucks, or petrol versus diesel vehicles) and reporting only one of them.

For the record, if you really care about greenhouse gas emissions you will switch off your lights, fridge and home air-conditioning immediately – coal burning for electricity creates 48 per cent of Australia’s greenhouse gas emissions. Agriculture accounts for 17 per cent. Cars? Seven per cent, by Australian Greenhouse Office figures.

—“One million and counting”, Sydney Morning Herald, 12 January 2008

This ‘seven per cent’ figure gained currency shortly after the election of the Rudd Labor Government in 2007, in an apparent attempt to portray transport as unworthy of inclusion in Rudd’s carbon trading scheme. (As the record shows, transport was indeed excluded from the Gillard carbon pricing scheme four years later.) It is obtained by dividing the emissions from road transport into passenger cars, light commercial vehicles, trucks and motorcycles, and singling out the figure for ‘passenger cars’ alone. Aside from the fact that many ‘light commercial’ vehicles are also used for personal transport, this sets up a misleading comparison involving the ‘non-commercial’ uses of road transport versus both the commercial and non-commercial uses of electricity.

(The SMH article also got the ‘electricity’ figure badly wrong, even by 2008 standards. 48 per cent was not the figure for electricity, but for all stationary energy use: it includes activities such as petrol refining, the main product of which is fuel for cars. Electricity actually represented about 36% of emissions in 2008, and about 31% a decade later.)

What happens if we look specifically at household emissions from electricity and gas use, alongside emissions from household transport activities? The CSIRO did this in 2002, and their results took many by surprise. Here transport emerges as by far the greatest energy user and the biggest factor in household greenhouse emissions.

ApplicationGreenhouse emissions
Tonnes per yearPercent
Hot Water3.312.0
Clothes Drying0.51.8
Other Appliances0.51.8

(Source: Australian Greenhouse Office / CSIRO: National Kilowatt Count of Household Energy Use, 2002)

So, if we were to avert climate change solely by reducing consumption we might tell people to switch off their lights, fridges and air conditioners, take cold showers and eat spoiled food in the dark—or we can give them a public transport alternative to driving, which would be more effective even if used by only one household member. Motor vehicle figures from the Bureau of Statistics show that the average Australian car, driven the average number of kilometres in a year, uses some 1700 litres of petrol and 16 megawatt-hours of energy: equivalent to around 30 four-star refrigerators, or 30 incandescent 60-watt lamps left running 24 hours a day for a year.

Nonetheless, it’s still true that households are only part of the global greenhouse emissions equation, so it’s the national aggregate figures that ultimately count. But what does it really mean to say that ‘electricity generation’ is the biggest source of emissions? Electricity has hundreds of different uses right across society (including much more for transport in the future), while on the other hand transport is only one of the many uses of oil. Moving ourselves and our goods around is just one activity among many that we do, but many of those other activities use energy. The real question is, which of these myriad activities should we focus our efforts on in order to get the most ‘bang per buck’?

A partial answer can be found in figures compiled by the government on energy use according to ‘economic sector’. This gives a very rough measure of the extent to which various kinds of activity consume energy and hence contribute to the majority of greenhouse emissions. Here are the figures for the 2004–05 financial year, which predate the Global Financial Crisis and the end of car manufacturing in Australia:

SectorEnergy consumption in petajoules
Trade and services249

(Source: ABS Year Book Australia 2007, from ABARE energy statistics.)

These figures reveal transport to be the single largest energy-consuming activity in Australia, responsible for over one-third of all energy use. It is rivalled only by manufacturing, which includes highly energy-intense activities such as aluminium smelting but still used less energy overall in 2004-05 than transport. More recent declines in manufacturing activity (such as the closure of aluminium smelters and automotive plants in Victoria) mean that transport will outrank all other economic sectors in energy use now and in the future even more than these figures suggest.

So however one frames the figures, there are sound reasons for focussing on the emissions due to transport. While it’s a matter of debate whether they’re the largest component of our emissions, there’s no doubt that they are one of the fastest-growing components. The National Greenhouse Gas Inventory shows that, while Australia’s emissions as a whole increased by 23 per cent between 1990 and 2003, transport-related emissions increased by almost 30 per cent over the same period. More recently, it has been found that transport emissions increased 34 per cent between 2001 and 2017, faster than any other source except LNG production.

Worldwide, a 2014 UN report (reported on here by Bloomberg) finds that motor vehicles are likely to be the fastest-growing source of greenhouse emissions right through to 2050 on current trends. Increases in transport emissions have been all but counteracting efforts to substitute renewable energy for fossil fuels in electricity generation: according to a 2019 report from ANU’s Hugh Saddler (reported in the Guardian), a 21.7 million tonne increase in diesel emissions in Australia between 2011 and 2018 all but wiped out the 22.1 million tonne reduction in electricity emissions over that time.

Shifting trips from private cars to public transport (and freight from trucks to trains) not only saves energy, but also reduces transport emissions substantially. The following representative figures for Melbourne peak hour conditions have been calculated from operating energy figures on our energy page, together with Federal Government figures for emissions from liquid fuels and from the 2020 Australian electricity grid.

Transport modeEnergy use
(MJ per
(g CO2-e per
Petrol Car3.4263
LPG Car3.4235
Ethanol (E10) Car3.4232
Electric Car (2020 grid)0.7130
Electric Car (100% renewable grid)0.70
Electric Tram (2020 grid)0.1530
Diesel Bus0.2822
Ethanol (E10) Bus0.2819
Natural Gas Bus0.2818
Diesel Train (V/Line)0.1814
Electric Train (2020 grid)0.048
250cc Motorcycle1.6124
1000cc Motorcycle2.3178

Source: Fuel emissions intensity figures from Australian Greenhouse Office, AGO Factors and Methods Workbook 2006. Electricity emissions intensity of 199g/MJ sourced from Office of the Clean Energy Regulator, Electricity sector emissions and generation data 2019-20.

Despite the fact that Melbourne trams already run from 100% renewable electricity and electric trains are set to follow, 2020 grid figures have been used above to emphasise that even assuming ‘worst case’ figures for emissions intensity, electric trains and trams have a fraction of the emissions per unit of output compared with internal-combustion cars (which still predominate in Australia’s fleet in the 2020s). For electric cars, the charging source is obviously critical: charged from the grid, the emissions are intermediate between internal-combustion cars and public transport, but with a 100% renewable grid the emissions for cars, trains and trams will all match at zero (at least for operation, if not for manufacture). Again, however, using public transport is a choice that many can make today (and many more could make soon, given only a decision to get more out of existing fleets and infrastructure). The most optimistic scenarios for electric cars see new internal-combustion sales ceasing between 2025 and 2030, and a further decade before the on-road fleet is nearly exclusively electric (and the grid 100% renewable).

But to sum up: notwithstanding the time it will take to electrify vehicle fleets and the electricity grid, there is no reason why transport-related emissions should be growing faster than almost any other component. In a world with genuine transport choices, one would actually expect the opposite. Where public transport is convenient and reliable, it is much easier to leave the car at home and save the energy than it is to rebuild one’s house to not require heating or cooling, or to install solar panels on the roof, or to replace all one’s appliances with the latest energy-efficient models—worthwhile as all these other actions are.

In any case, if one is faced with the task of reducing greenhouse emissions across all activities in a society, it seems fairest and least harmful to share the burden equally, and plan for the same reduction in transport energy use as in other areas where we use energy. This was the conclusion reached by the Garnaut Review on greenhouse mitigation, even if it’s been ignored by all Federal Governments since. But the first priority would have to be to stop our transport emissions growing faster than any other. Transport planning that focusses on sustainable modes rather than the car-dependent status quo will help.

Last modified: 21 October 2021