Street-network Sprawl in Nanxi, China

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.

Nanxi: city in Sichuan, China

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 Nanxi, China on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Nanxi as of 2014, the overall level of street-network sprawl is 1.55, which is relatively well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 3.39, 1.53, nan and -0.16. Data was not available in 1991-2000.

Quantity of street network construction: The street network in Nanxi spans a total of 83 kilometers. It is dominated by roads constructed in 2001-2014. These roads have an SNDi of -0.16, which is very 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 3.39, 2.54, 2.42 and 1.55. Overall, the SNDi of the aggregate street network has fallen: the street network in Nanxi has become more connected. This decrease has quickened: between 1975 and 1976-1990, SNDi fell by 0.85 points, but between 1991-2000 and 2001-2014, it fell by just 0.87.

Nanxi and Sichuan do not follow the same trend in the disconnectivity of their street network constructions. There was not enough data from the city, while the SNDi of street constructions in Sichuan was at its lowest in 1991-2000.

How do development practices in Nanxi fare in comparison to others in Sichuan? Most recently in 2001-2014, street construction in Nanxi was the 78th-most disconnected out of the 102 cities in Sichuan. Its position in the ranks since 1975 has fallen; relative to other cities in Sichuan, street construction in Nanxi has become more connected. Nanxi ranked 21st in 1975, 51st in 1976-1990 and 78th in 2001-2014. There was no ranking in 1991-2000 due to unavailable data.

Nanxi and China do not follow the same trend in the disconnectivity of their street network constructions. There was not enough data from the city, while the SNDi of street constructions in China followed a zig-zag trend with an overall decrease.

How do development practices in Nanxi fare in comparison to others in China? Most recently in 2001-2014, street construction in Nanxi was the 1309th-most disconnected out of the 1651 cities in China. Its position in the ranks since 1975 has fallen; relative to other cities in China, street construction in Nanxi has become more connected. Nanxi ranked 176th in 1975, 856th in 1976-1990 and 1309th in 2001-2014. There was no ranking in 1991-2000 due to unavailable data.

Nanxi and Sichuan do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Nanxi fell steadily, while the SNDi of street constructions in Sichuan was at its lowest in 1991-2000.

To date, Nanxi is the 69th-most disconnected out of the 102 cities in Sichuan. Its position in the ranks since 1975 has fallen; relative to other cities in Sichuan, the street network in Nanxi has become more connected. Nanxi ranked 21st in 1975, 41st in 1976-1990, 42nd in 1991-2000 and 69th in 2001-2014.

Nanxi and China do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Nanxi fell steadily, while the SNDi of street constructions in China peaked in 1976-1990.

To date, Nanxi is the 934th-most disconnected out of the 1651 cities in China. Its position in the ranks since 1975 has fallen; relative to other cities in China, the street network in Nanxi has become more connected. Nanxi ranked 176th in 1975, 435th in 1976-1990, 469th in 1991-2000 and 934th in 2001-2014.

As of 2015, Nanxi had a built-up area of 5.26 square kilometers, and a population of 98209 people.

These are some other cities with approximately the same population: