Street-network Sprawl in Zigong, 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.

Zigong: 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 Zigong, China on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Zigong as of 2014, the overall level of street-network sprawl is 2.9, which is in the 40th to 60th percentile of disconnectedness.

Trends in street network construction: The SNDis of street construction for the respective time periods are 3.83, 3.27, 1.31 and 0.87. In each period, new street development in Zigong steadily grows more connected than in the last.

Quantity of street network construction: The street network in Zigong spans a total of 375 kilometers. It is dominated by roads constructed in 2001-2014. These roads have an SNDi of 0.87, 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 3.83, 3.72, 3.34 and 2.9. Overall, the SNDi of the aggregate street network has fallen: the street network in Zigong has become more connected. This decrease has quickened: between 1975 and 1976-1990, SNDi fell by 0.11 points, but between 1991-2000 and 2001-2014, it fell by just 0.44.

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

How do development practices in Zigong fare in comparison to others in Sichuan? Most recently in 2001-2014, street construction in Zigong was the 70th-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 Zigong has become more connected. Zigong ranked 12th in 1975, 18th in 1976-1990, 41st in 1991-2000 and 70th in 2001-2014.

Zigong and China do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Zigong fell steadily, while the SNDi of street constructions in China followed a zig-zag trend with an overall decrease.

How do development practices in Zigong fare in comparison to others in China? Most recently in 2001-2014, street construction in Zigong was the 1048th-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 Zigong has become more connected. Zigong ranked 119th in 1975, 251st in 1976-1990, 681st in 1991-2000 and 1048th in 2001-2014.

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

To date, Zigong is the 32nd-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 Zigong has become more connected. Zigong ranked 12th in 1975, 14th in 1976-1990, 21st in 1991-2000 and 32nd in 2001-2014.

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

To date, Zigong is the 326th-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 Zigong has become more connected. Zigong ranked 119th in 1975, 134th in 1976-1990, 182nd in 1991-2000 and 326th in 2001-2014.

As of 2015, Zigong had a built-up area of 28.67 square kilometers, and a population of 533623 people.

These are some other cities with approximately the same population: