Increased traffic


Both population and economic growth typically cause increased traffic, which can increase traffic congestion. Unless mitigated, traffic congestion tends to increase more quickly than the growth rates in the underlying drivers, because of the compounding effect that additional traffic has on traffic congestion. Although estimating future traffic congestion can be difficult and complex because of the assumptions that need to be made, in 2009, the Bureau of Transport and Regional Economics projected a baseline increase in the avoidable social cost of congestion (see Section 2.1.3) of 117% between 2005 and 2020, compared with a projected increase of 37% in total annual kilometres travelled in passenger-car equivalent units.14 In comparison, the mid-range population projections in the 2010 intergenerational report produced by the Australian Government Treasury are for a population increase of 26% between 2005 and 2020.35 Using that report's projected economic growth rate (an average annual increase of 2.7% in gross domestic product [GDP]), GDP would increase by 49% over the same period. However, as noted in Section 2, traffic has recently levelled off in major Australian cities (associated with reduced private vehicle kilometres travelled per person); if it continues, this trend would reduce future growth in congestion.

Harper P (2011). Built environment: Increased traffic. In: Australia state of the environment 2011, Australian Government Department of the Environment and Energy, Canberra,, DOI 10.4226/94/58b65a5037ed8