Street-network Sprawl in Dunedin, New Zealand

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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:

• nodal degree
• dendricity, the tree-likeness of the street network
• circuity, the ratio of the distance by road to the straight-line distance of two locations on the street network
• sinuosity, the curviness of a street

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:

• Global trends toward urban street-network sprawl
• A global assessment of street-network sprawl

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

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Dunedin: city in Otago, 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 Dunedin, New Zealand on the sprawlmap

How have Dunedin's street networks changed over time?

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Dunedin as of 2014, the overall level of street-network sprawl is 1.7, which is relatively well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 1.69, nan, nan and nan. Data was not available in 1976-1990, 1991-2000 and 2001-2014.

Quantity of street network construction: The street network in Dunedin spans a total of 409 kilometers. It is dominated by roads constructed prior to 1975. These roads have an SNDi of 1.69, which is relatively well-connected.

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 1.69, 1.69, 1.7 and 1.7. Overall, the SNDi of the aggregate street network has risen: the street network in Dunedin has become more disconnected.

Dunedin in context: Street-network sprawl of new development

Dunedin and Otago do not follow the same trend in the disconnectivity of their street network constructions. There was not enough data from the city, as well as the Otago's street network construction.

How do development practices in Dunedin fare in comparison to others in Otago? out of the 1 cities in Otago. Dunedin ranked 1st in 1975. There was no ranking in 1976-1990, 1991-2000, and 2001-2014 due to unavailable data.

Dunedin and New Zealand do not follow the same trend in the disconnectivity of their street network constructions. There was not enough data from the city, as well as the New Zealand's street network construction.

How do development practices in Dunedin fare in comparison to others in New Zealand? out of the 8 cities in New Zealand. Dunedin ranked 8th in 1975. There was no ranking in 1976-1990, 1991-2000, and 2001-2014 due to unavailable data.

Dunedin in context: Aggregate street-network sprawl

Dunedin and Otago do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Dunedin rose steadily, while the SNDi of street constructions in Otago rose steadily.

To date, Dunedin is the 1st-most disconnected out of the 1 cities in Otago. Its position in the ranks since 1975 has not changed. Dunedin ranked 1st in 1975, 1st in 1976-1990, 1st in 1991-2000 and 1st in 2001-2014.

Dunedin and New Zealand do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Dunedin rose steadily, while the SNDi of street constructions in New Zealand rose steadily.

To date, Dunedin is the 8th-most disconnected out of the 8 cities in New Zealand. Its position in the ranks since 1975 has not changed. Dunedin ranked 8th in 1975, 8th in 1976-1990, 8th in 1991-2000 and 8th in 2001-2014.

What about other similarly-populated cities?

As of 2015, Dunedin had a built-up area of 12.59 square kilometers, and a population of 70726 people.

These are some other cities with approximately the same population:

• Bandırma, Turkey
• Unjon, North Korea
• Togh, Pakistan