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CARA Data Assets: Technical description

Context

The time and distance it takes to travel to the services is one of the core characteristics of the built environment. Many of the key decisions people make, such as the purchase of a home, revolve around access to the education, health and government services they rely on.
Detailed and accurate measures of access to services are important to understanding of the supply and demand for services and central to the development of policy to fairly distribute  services across a population.

The Centre for Australian Research into Access (CARA) has applied modern data and computing processing techniques to develop infrastructure that rapidly calculates access to services metrics for every Australian private dwelling. Further, CARA has developed spatial micro-simulation models to simulates people, families and households within these dwellings, which allows access to different services to be evaluated for different groups of the Australian population.

The ability to calculate metrics directly from every dwelling in Australia to the building within which a service is located, allows CARA to produce metrics that are independent of any arbitrary spatial unit and therefore can be aggregated to any type of area, be it statistical, administrative or environmental. This allows these metrics to be free from the statistical biases and constraints imposed by arbitrarily aggregation such as the Modifiable Areal Unit Problem (MAUP) and the Ecological Fallacy (Openshaw, 1984).

Calculation Process

The inputs to the CARA time/distance metrics are;

  • A collection of starting points or origins from which to measures are made.
  • A network of lines composed of nodes and segments that model the topology (connectiveness), restrictions (one/two-way, overpasses etc.) and traffic speeds associated with the Australian road network.
  • A collection of end points or destinations (services) to which measure are made.

The origins (dwelling locations) are derived from the CARA Dwelling Location Reference Frame (DLRF). This is a modelled data set that is derived from the 2021 Australian Census of Population & Housing’s mesh block count of private dwellings which are distributed to individual building footprints based on a range of criteria tailored to the nature of the mesh block.

The destinations (service locations) are sourced from either national registers or from commercially curated data sets of points of interest, when no official sources are available.

The network topologically models the roads, junctions, and traffic directions & restrictions of the physical road system. Each road segment is associated with an impedance (distance, speed). CARA uses two sources of road network data.

  1. The Street Pro Navigation product from Precisely Ltd
  2. The the Transportation Theme from Overture Maps Foundation

Data on road speeds is derived through aggregate measurement of active vehicles by TomTom. Time is derived from the minimum speeds during either the morning or evening peak periods.

Shortest time/distance network times and distances are calculated by traversing the network using the Dijkstra’s algorithm which is enhanced by applying a Contraction Hierarchy heuristic. This algorithm is implemented in C++ and enabled as a Python library called Pandana. Pandana it was developed by UrbanSim at the University of Berkley (Foti & Waddell, 2012)
The Pandana library operates by linking the point location of origins (and destinations) to their nearest node on the network. The distance of this straight line is derived, and the associated time is calculated based on a mean speed value across the whole of the network (20km/h). These times and distances are added to each of the shortest routes calculated by Pandana.

References

Foti, F., Waddell, P. & Luxen, D., (2012) A Generalized Computational Framework for Accessibility: From the Pedestrian to the Metropolitan Scale., Transportation Research Board Annual Conference.
Openshaw, S. (1984). Ecological Fallacies and the Analysis of Areal Census Data. Environment and Planning A: Economy and Space, 16(1), 17-31. https://doi.org/10.1068/a160017
Openshaw, S. (1984), The Modifiable Areal Unit Problem, Concepts and Techniques in Modern Geography, Geobooks.

Deakin Rural Health

Deakin Rural Health (DRH) was established in 2016 and is part of the Deakin University School of Medicine within the Faculty of Health. DRH is a University Department of Rural Health funded through the Rural Health Multidisciplinary Training (RHMT) program – an initiative of the Australian Government Department of Health and Aged Care. The RHMT program aims to improve the recruitment and retention of medical, nursing, dental and allied health professionals in rural and remote Australia. Alongside this is an emphasis on research capability and capacity building. In responding to this need, DRH is focussed on producing insights that are both policy relevant and at scale to improve decision-making and resource allocation.

Grampians Health

Grampians Health was established 1 November 2021 and brings together Edenhope and District Memorial Hospital, Stawell Regional Health, Wimmera Health Care Group and Ballarat Health Services. The Grampians Region extends from Bacchus Marsh to the South Australian border, covering some 48,000m2, and is home to nearly 250,000 people.

Grampians Health delivers care across all settings: in hospital and increasingly in the community and people’s homes. It is the largest public provider of residential aged care in Australia. Additionally, Grampians Health is the main teaching, training and research provider in the region and does this through affiliations with its partner universities and teaching institutions.

CARA Directors & Researchers

Professor Vincent Versace

Co-Director of CARA and Director of Deakin Rural Health
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Associate Professor Anna Wong Shee

Co-Director CARA
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Associate Professor Kevin Mc Namara

Deputy Director (Research), Deakin Rural Health
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Professor Neil Coffee

Professor Health Geography
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Philip Roberts

Professor Philip Roberts

Professor Curriculum Inquiry and Rural Education
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Professor Rob Tanton

Professor of Spatial Microsimulation
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Dr Jesse Whitehead

Senior Research Fellow, University of Waikato, New Zealand
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Mr Ralf-Dieter Schroers

Geospatial Data Scientist
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Mr Marcus Blake

Technical Manager
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Ms Sarah Wood

Associate Research Fellow
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Mr Sam Quinsey

Associate Research Fellow
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