Motor vehicles emit a wide range of pollutants from their tailpipes, and are a major source of nitrogen oxides (NOx) and carbon monoxide (e.g. Figure ATM30). These are supplemented by non-tailpipe emissions such as brake, tyre and road-wear particles, which will become the dominant vehicle emissions as engine emissions standards are tightened. Total vehicle kilometres travelled increased by an average of 1.9 per cent per year from 2010 to 2014. Although distance travelled by vehicles is, to some extent, mitigated by improving emissions standards, it continues to put pressure on air quality. As at 31 October 2014, the annual vehicle kilometres travelled for all road vehicles in Australia were estimated at 244 billion kilometres. Of this, 179 billion occurred in capital city and urban areas (ABS 2014a). Furthermore, total metropolitan vehicle kilometres travelled are projected to increase by 41 per cent from 2015 to 2030 (BITRE 2015).
Average growth in urban public transport was particularly strong between 2005 and 2009, with total patronage (summed across all 8 capitals) increasing by about 4.7 per cent per year. Growth in the past few years has been lower, averaging around 1.3 per cent per year between 2009 and 2013 (BITRE 2014).