Street-network Sprawl in New South Wales, Australia

What is Street-network sprawl?

Street-network Sprawl is a way to measure urban sprawl, worldwide, through the connectedness of the streets. Less sprawl means more connected, more walkable streets. Well-connected streets – like New York City’s grid – are more walkable and can be served by public transit.

The street network is permanent, and its connectivity affects the livability and environmental footprint of cities for decades and centuries to come. In places with more connected streets, residents drive less and walk more. A well-connected street network is associated with better outcomes for health, the environment, sustainable consumption, social integration, and equity.

We can quantify how connected street networks are with the Street Network Disconnectedness Index (SNDi).

SNDi -- our measure of street-network sprawl (disconnectedness)

The SNDi is a comprehensive measurement of “sprawl”. It captures:

A higher SNDi means less-connected streets – i.e., more sprawl. For the 10137 cities in our dataset, the average SNDi is 2.25, with half of the cities' SNDis falling between 1.08 and 3.25.

More information on the sprawl index can be found in these research papers:

To see the state of street-network sprawl across the globe, visit the sprawlmap.

New South Wales: region in Australia

What exactly constitutes the spatial extent of the city? For these aggregations, we used the Global Human Settlement Layer Urban Center Database (GHS-UCDB) to define the boundaries of the city. These cities -- or urban centers -- cover areas that are densely populated and built-up, and so may extend beyond the spatial borders of these cities that we may be familiar with. The GHS area is shaded in blue.

View New South Wales, Australia on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in New South Wales as of 2014, the overall level of street-network sprawl is 4.06, which is highly disconnected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 3.07, 5.28, 6.11 and 5.68. Street construction in New South Wales increased in disconnectivity initially but has since improved. The streets constructed in 1991-2000 were the most disconnected.

Quantity of street network construction: The street network in New South Wales spans a total of 80917 kilometers. The period with the greatest volume of street construction was 1975. These roads have an SNDi of 3.07, which is in the 40th to 60th percentile of disconnectedness.

Effect on the aggregate network: New construction in each period adds to the total stock of streets, but does not change streets that have already been built. Therefore, it has a limited effect on the street network as a whole. The SNDis of the aggregate street network in the respective time periods are 3.07, 3.74, 3.93 and 4.06. Overall, the SNDi of the aggregate street network has risen: the street network in New South Wales has become more disconnected. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 0.68 points, but between 1991-2000 and 2001-2014, it rose by just 0.13.

The level of street-network sprawl in new development in New South Wales peaked in 1991-2000. To get a sense of how street development has changed in New South Wales, we can consider three of its most populous cities: Sydney, Newcastle and Wollongong. Out of the three cities, Sydney and Newcastle do not follow the same trend as the region. The level of street-network sprawl in new development in Sydney peaked in 1976-1990. The level of street-network sprawl in new development in Newcastle peaked in 1976-1990.

How do development practices in New South Wales fare in comparison to others in Australia? Most recently in 2001-2014, street construction in New South Wales was the 3rd-most disconnected out of the 7 regions in Australia. Its position in the ranks since 1975 has fallen; relative to other regions in Australia, street construction in New South Wales has become more connected. New South Wales ranked 2nd in 1975, 2nd in 1976-1990, 3rd in 1991-2000 and 3rd in 2001-2014.

As of 2014, the city with the most disconnected street network in New South Wales is Campbelltown with an SNDi of 4.75, which is highly disconnected. Conversely, the most connected city is Newcastle with an SNDi of 2.82, which is in the 40th to 60th percentile of disconnectedness. See trends for these cities: Newcastle, Campbelltown

The level of street-network sprawl in the aggregate network in New South Wales rose steadily. To get a sense of how the aggregate street network has changed in New South Wales, we can consider three of its most populous cities: Sydney, Newcastle and Wollongong. Disconnectivity in the most populous cities in New South Wales follow the same region trend.

To date, New South Wales is the 3rd-most disconnected out of the 7 regions in Australia. Its position in the ranks since 1975 has fallen; relative to other regions in Australia, the street network in New South Wales has become more connected. New South Wales ranked 2nd in 1975, 3rd in 1976-1990, 3rd in 1991-2000 and 3rd in 2001-2014.