Industrialised nations witnessed a substantial growth in private motor vehicles from the 1970s onwards. However, since the late 2000s, many of these countries have seen a plateau, and in some cases, a decline in car use. There are a number of reasons for this shift, including changes to urban form and structure, emphases on the environmental impacts on car use, rising fuel costs and the growth of public and active transport modes. Another dimension of this shift, in addition to overall decline in car use, is the adoption of much higher fuel efficiencies within the private motor vehicle fleet, which have accelerated in jurisdictions where declines in car travel are most prominent. Very few urban transport studies have explored the social and spatial outcomes of these changes, both on transport behaviours and on the vulnerability of urban communities to future shifts in oil prices, especially at a metropolitan scale.

Dr. Tiebei Li and Professor Jago Dodson from the Centre for Urban Research at RMIT, together with Professor Neil Sipe from the University of Queensland investigated the changes in the urban private vehicle efficiency in Brisbane, using novel green vehicle datasets constructed for 2009 and 2014. Dr. Li and his colleagues examined the spatial changes to vehicle fuel efficiencies in Brisbane over this period, investigating how those changes intersected with oil price vulnerability. They also modelled, within an explicitly spatial context, how changes to vehicle fuel efficiencies would improve household travel budgets, and examined how a stronger fuel economy policy could influence future household vehicle ownership choices.

The results of this study showed that vehicle fuel efficiency changes have been uneven over Brisbane. Inner urban areas experienced a larger change in vehicle fuel efficiency, while outer suburbs showed a much lower tendency to shift to more efficient vehicles. However, the authors showed that although the shifts were smaller in the outer, more oil-vulnerable suburbs, the impacts on household budgets from these more modest changes are still likely to be significant, given the longer journeys and higher level of fuel consumption in those areas. Overall, the outer suburbs of Brisbane experienced an average of fuel savings over a five year period that was 46% greater than the inner and middle suburbs, even though uptake of fuel-efficient vehicles was higher in those areas. The authors were also able to show that imposing a stronger national fuel economy target in the long term would accelerate evolution of vehicle fleets and oil vulnerability reduction in Brisbane, and likely in other Australian urban areas as well.