Street-network Sprawl in Suzhou, 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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Suzhou: city in Jiangsu, 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 Suzhou, China on the sprawlmap

How have Suzhou's street networks changed over time?

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Suzhou as of 2014, the overall level of street-network sprawl is 2.4, 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 1.69, 2.51, 2.25 and 2.58. Disconnectivity in street construction in Suzhou follows a zig-zag trend. In 1975, street construction was most disconnected, while construction was most connected in 2001-2014.

Quantity of street network construction: The street network in Suzhou spans a total of 11714 kilometers. It is dominated by roads constructed in 2001-2014. These roads have an SNDi of 2.58, 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 1.69, 2.27, 2.25 and 2.4. Disconnectivity in Suzhou's street network follows a zig-zag trend. In 1975, the city was most disconnected; while it was most connected in 2001-2014.

Suzhou in context: Street-network sprawl of new development

Suzhou and Jiangsu follow the same trend in the disconnectivity of their street network constructions. The SNDi for both of these followed a zig-zag trend with an overall increase.

How do development practices in Suzhou fare in comparison to others in Jiangsu? Most recently in 2001-2014, street construction in Suzhou was the 17th-most disconnected out of the 87 cities in Jiangsu. Its position in the ranks since 1975 has risen; relative to other cities in Jiangsu, street construction in Suzhou has become more disconnected. Suzhou ranked 35th in 1975, 25th in 1976-1990, 28th in 1991-2000 and 17th in 2001-2014.

Suzhou and China follow the same trend in the disconnectivity of their street network constructions. The SNDi for both of these followed a zig-zag trend with an overall increase.

Suzhou in context: Aggregate street-network sprawl

Suzhou and Jiangsu do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Suzhou followed a zig-zag trend with an overall increase, while the SNDi of street constructions in Jiangsu peaked in 1976-1990.

To date, Suzhou is the 22nd-most disconnected out of the 87 cities in Jiangsu. Its position in the ranks since 1975 has risen; relative to other cities in Jiangsu, the street network in Suzhou has become more disconnected. Suzhou ranked 35th in 1975, 25th in 1976-1990, 25th in 1991-2000 and 22nd in 2001-2014.

Suzhou and China do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Suzhou followed a zig-zag trend with an overall increase, while the SNDi of street constructions in China peaked in 1976-1990.

What about other similarly-populated cities?

As of 2015, Suzhou had a built-up area of 913.62 square kilometers, and a population of 8625178 people.

These are some other cities with approximately the same population:

• New Taipei [Taipei], Taiwan
• Bogota, Colombia
• Surabaya, Indonesia