Street-network Sprawl in Tongliang, 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.

Tongliang: city in Chongqing, 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 Tongliang, China on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Tongliang as of 2014, the overall level of street-network sprawl is 1.6, which is relatively well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are -0.69, 1.08, 1.2 and 2.2. In each period, new street development in Tongliang steadily grows more disconnected than in the last. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 1.77 points, but between 1991-2000 and 2001-2014, it rose by just 0.99.

Quantity of street network construction: The street network in Tongliang spans a total of 177 kilometers. It is dominated by roads constructed in 2001-2014. These roads have an SNDi of 2.2, 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 -0.69, 0.86, 1.12 and 1.6. Overall, the SNDi of the aggregate street network has risen: the street network in Tongliang has become more disconnected. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 1.56 points, but between 1991-2000 and 2001-2014, it rose by just 0.48.

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

How do development practices in Tongliang fare in comparison to others in Chongqing? Most recently in 2001-2014, street construction in Tongliang was the 26th-most disconnected out of the 38 cities in Chongqing. Its position in the ranks since 1975 has fallen; relative to other cities in Chongqing, street construction in Tongliang has become more connected. Tongliang ranked 23rd in 1975, 25th in 1976-1990, 22nd in 1991-2000 and 26th in 2001-2014.

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

How do development practices in Tongliang fare in comparison to others in China? Most recently in 2001-2014, street construction in Tongliang was the 602nd-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 Tongliang has become more disconnected. Tongliang ranked 1232nd in 1975, 1039th in 1976-1990, 719th in 1991-2000 and 602nd in 2001-2014.

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

To date, Tongliang is the 30th-most disconnected out of the 38 cities in Chongqing. Its position in the ranks since 1975 has fallen; relative to other cities in Chongqing, the street network in Tongliang has become more connected. Tongliang ranked 23rd in 1975, 28th in 1976-1990, 30th in 1991-2000 and 30th in 2001-2014.

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

To date, Tongliang is the 907th-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 Tongliang has become more disconnected. Tongliang ranked 1232nd in 1975, 1198th in 1976-1990, 1095th in 1991-2000 and 907th in 2001-2014.

As of 2015, Tongliang had a built-up area of 8.27 square kilometers, and a population of 161208 people.

These are some other cities with approximately the same population: