Motor vehicles are a significant source of anthropogenic CO2 emissions in Australia, comprising some 90 per cent of transport CO2 emissions, which made up 17 per cent of Australia’s net CO2-equivalent emissions in 2015 (see Sectoral emissions). However, despite their contribution to climate change, the most immediate threat posed by motor vehicles is to air quality. As a proportion of emissions in the NPI, vehicles account for around 40 per cent of emissions of carbon monoxide, 41 per cent of VOCs, 18 per cent of NOx and 17 per cent of fine particles (as PM2.5). It is expected that a more coordinated approach to reduce the health and environmental impacts from motor vehicle emissions will be delivered by the Ministerial Forum on Motor Vehicle Emissions, established in 2015. The forum is investigating ways to improve the energy productivity of transport, improve air quality and reduce greenhouse gas emissions.
From 2011 to 2016, motor vehicle registrations increased by 12.2 per cent (averaging 2.3 per cent annually), which was slightly lower than the 15.4 per cent growth in the previous 5 years. The bulk of this growth was in passenger vehicles, which make up 75 per cent of the total Australian fleet. As noted earlier in this report, despite significant growth in vehicle numbers and distances travelled (which increased by an average 1.9 per cent per year between 2010 and 2014), advances in motor vehicle engine and emissions control technology (together with improved fuel standards) have driven down emissions of carbon monoxide and VOCs. Projections to 2020 show these gains being maintained and levels of NOx declining. (These projections are based on a ‘business as usual’ scenario, which does not factor in the progressive application of likely tighter emissions control standards, which should reinforce the projected gains.) However, non-tailpipe particle emissions such as brake and tyre wear are projected to become an increasing proportion of total vehicle emissions in the future.
The threat, however, is that the combination of increasing vehicle numbers, distance travelled and congestion (which leads to more exhaust and evaporative emissions) may cancel out gains in technology, resulting in increased impacts on health and reduced amenity. For example, emerging concerns in Europe about increases in vehicle emissions of NO2 accompanying technology-driven reductions in NOx could foreshadow similar concerns in Australia as the proportion of diesel vehicles in the fleet continues to grow. The number of diesel-fuelled registered vehicles grew at 10 per cent per year from 2010 to 2015; at 31 January 2016, they made up 20.9 per cent of all registered vehicles.