Street-network Sprawl in Tiandong County, 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.

Tiandong County: city in Guangxi, 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 Tiandong County, China on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Tiandong County as of 2014, the overall level of street-network sprawl is 3.67, which is highly disconnected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 3.55, 4.17, 3.5 and 5.87. Disconnectivity in street construction in Tiandong County follows a zig-zag trend. In 1991-2000, street construction was most disconnected, while construction was most connected in 2001-2014.

Quantity of street network construction: The street network in Tiandong County spans a total of 132 kilometers. It is dominated by roads constructed prior to 1975. These roads have an SNDi of 3.55, which is highly disconnected.

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 3.55, 3.57, 3.57 and 3.67. Disconnectivity in Tiandong County's street network follows a zig-zag trend. In 1975, the city was most disconnected; while it was most connected in 2001-2014.

Tiandong County and Guangxi 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 Tiandong County fare in comparison to others in Guangxi? Most recently in 2001-2014, street construction in Tiandong County was the 4th-most disconnected out of the 53 cities in Guangxi. Its position in the ranks since 1975 has not changed. Tiandong County ranked 4th in 1975, 5th in 1976-1990, 11th in 1991-2000 and 4th in 2001-2014.

Tiandong County 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.

How do development practices in Tiandong County fare in comparison to others in China? Most recently in 2001-2014, street construction in Tiandong County was the 52nd-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 Tiandong County has become more disconnected. Tiandong County ranked 153rd in 1975, 121st in 1976-1990, 172nd in 1991-2000 and 52nd in 2001-2014.

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

To date, Tiandong County is the 9th-most disconnected out of the 53 cities in Guangxi. Its position in the ranks since 1975 has fallen; relative to other cities in Guangxi, the street network in Tiandong County has become more connected. Tiandong County ranked 4th in 1975, 6th in 1976-1990, 9th in 1991-2000 and 9th in 2001-2014.

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

To date, Tiandong County is the 146th-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 Tiandong County has become more disconnected. Tiandong County ranked 153rd in 1975, 159th in 1976-1990, 142nd in 1991-2000 and 146th in 2001-2014.

As of 2015, Tiandong County had a built-up area of 3.67 square kilometers, and a population of 64906 people.

These are some other cities with approximately the same population: