Street-network Sprawl in Yizhen, 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.

Yizhen: 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 Yizhen, China on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Yizhen as of 2014, the overall level of street-network sprawl is 2.15, which is relatively well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 1.31, 1.5, 1.71 and 3.12. In each period, new street development in Yizhen steadily grows more disconnected than in the last.

Quantity of street network construction: The street network in Yizhen spans a total of 280 kilometers. It is dominated by roads constructed in 2001-2014. These roads have an SNDi of 3.12, 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 1.31, 1.4, 1.41 and 2.15. Overall, the SNDi of the aggregate street network has risen: the street network in Yizhen has become more disconnected.

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

How do development practices in Yizhen fare in comparison to others in Jiangsu? Most recently in 2001-2014, street construction in Yizhen was the 8th-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 Yizhen has become more disconnected. Yizhen ranked 43rd in 1975, 48th in 1976-1990, 38th in 1991-2000 and 8th in 2001-2014.

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

How do development practices in Yizhen fare in comparison to others in China? Most recently in 2001-2014, street construction in Yizhen was the 354th-most disconnected out of the 1651 cities in China. Its position in the ranks since 1975 has risen; relative to other cities in China, street construction in Yizhen has become more disconnected. Yizhen ranked 720th in 1975, 870th in 1976-1990, 577th in 1991-2000 and 354th in 2001-2014.

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

To date, Yizhen is the 27th-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 Yizhen has become more disconnected. Yizhen ranked 43rd in 1975, 48th in 1976-1990, 49th in 1991-2000 and 27th in 2001-2014.

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

To date, Yizhen is the 636th-most disconnected out of the 1651 cities in China. Its position in the ranks since 1975 has risen; relative to other cities in China, the street network in Yizhen has become more disconnected. Yizhen ranked 720th in 1975, 935th in 1976-1990, 950th in 1991-2000 and 636th in 2001-2014.

As of 2015, Yizhen had a built-up area of 25.61 square kilometers, and a population of 198111 people.

These are some other cities with approximately the same population: