Street-network Sprawl in Manawatu-Wanganui, New Zealand

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.

Manawatu-Wanganui: region in New Zealand

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 Manawatu-Wanganui, New Zealand on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Manawatu-Wanganui as of 2014, the overall level of street-network sprawl is 4.33, which is highly disconnected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 4.19, nan, 5.91 and 6.74. Data was not available in 1976-1990.

Quantity of street network construction: The street network in Manawatu-Wanganui spans a total of 4796 kilometers. It is dominated by roads constructed prior to 1975. These roads have an SNDi of 4.19, which is highly disconnected.

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 4.19, 4.19, 4.23 and 4.33. Overall, the SNDi of the aggregate street network has risen: the street network in Manawatu-Wanganui has become more disconnected.

The level of street-network sprawl in new development in Manawatu-Wanganui followed a zig-zag trend with an overall increase. To get a sense of how street development has changed in Manawatu-Wanganui, we can consider one of its most populous cities: Palmerston North. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in new development in Palmerston North followed a zig-zag trend with an overall increase.

How do development practices in Manawatu-Wanganui fare in comparison to others in New Zealand? Most recently in 2001-2014, street construction in Manawatu-Wanganui was the 3rd-most disconnected out of the 7 regions in New Zealand. Its position in the ranks since 1975 has risen; relative to other regions in New Zealand, street construction in Manawatu-Wanganui has become more disconnected. Manawatu-Wanganui ranked 4th in 1975, 4th in 1991-2000 and 3rd in 2001-2014. There was no ranking in 1976-1990 due to unavailable data.

As of 2014, the city with the most disconnected street network in Manawatu-Wanganui is Palmerston North with an SNDi of 3.57, which is highly disconnected. Conversely, the most connected city is Palmerston North with an SNDi of 3.57, which is highly disconnected. See trends for these cities: Palmerston North, Palmerston North

The level of street-network sprawl in the aggregate network in Manawatu-Wanganui rose steadily. To get a sense of how the aggregate street network has changed in Manawatu-Wanganui, we can consider one of its most populous cities: Palmerston North. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in the aggregate network in Palmerston North rose steadily.

To date, Manawatu-Wanganui is the 4th-most disconnected out of the 7 regions in New Zealand. Its position in the ranks since 1975 has not changed. Manawatu-Wanganui ranked 4th in 1975, 4th in 1976-1990, 4th in 1991-2000 and 4th in 2001-2014.