Street-network Sprawl in Zhongshan, China

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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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Zhongshan: city in Guangdong, 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 Zhongshan, China on the sprawlmap

How have Zhongshan's street networks changed over time?

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Zhongshan as of 2014, the overall level of street-network sprawl is 2.64, 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 2.14, 2.18, 2.65 and 3.9. In each period, new street development in Zhongshan steadily grows more disconnected than in the last.

Quantity of street network construction: The street network in Zhongshan spans a total of 1930 kilometers. The period with the greatest volume of street construction was 1991-2000. These roads have an SNDi of 2.65, 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 2.14, 2.17, 2.37 and 2.64. Overall, the SNDi of the aggregate street network has risen: the street network in Zhongshan has become more disconnected.

Zhongshan in context: Street-network sprawl of new development

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

How do development practices in Zhongshan fare in comparison to others in Guangdong? Most recently in 2001-2014, street construction in Zhongshan was the 21st-most disconnected out of the 109 cities in Guangdong. Its position in the ranks since 1975 has risen; relative to other cities in Guangdong, street construction in Zhongshan has become more disconnected. Zhongshan ranked 35th in 1975, 53rd in 1976-1990, 21st in 1991-2000 and 21st in 2001-2014.

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

Zhongshan in context: Aggregate street-network sprawl

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

To date, Zhongshan is the 34th-most disconnected out of the 109 cities in Guangdong. Its position in the ranks since 1975 has risen; relative to other cities in Guangdong, the street network in Zhongshan has become more disconnected. Zhongshan ranked 35th in 1975, 49th in 1976-1990, 42nd in 1991-2000 and 34th in 2001-2014.

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

What about other similarly-populated cities?

As of 2015, Zhongshan had a built-up area of 94.77 square kilometers, and a population of 1133016 people.

These are some other cities with approximately the same population:

• Saharanpur, India
• Yerevan, Armenia
• Berhampore, India