Street-network Sprawl in Gangu, 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.

Gangu: city in Gansu, 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 Gangu, China on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Gangu as of 2014, the overall level of street-network sprawl is 2.97, 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 2.0, 3.9, -0.01 and 1.65. Disconnectivity in street construction in Gangu follows a zig-zag trend. In 1991-2000, street construction was most disconnected, while construction was most connected in 1976-1990.

Quantity of street network construction: The street network in Gangu spans a total of 165 kilometers. It is dominated by roads constructed in 1976-1990. These roads have an SNDi of 3.9, 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 2.0, 3.1, 3.08 and 2.97. The aggregate street network in Gangu increased in disconnectivity initially,but the trend has turned around after 1990.

Gangu and Gansu do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Gangu followed a zig-zag trend with an overall decrease, while the SNDi of street constructions in Gansu was at its lowest in 1991-2000.

How do development practices in Gangu fare in comparison to others in Gansu? Most recently in 2001-2014, street construction in Gangu was the 22nd-most disconnected out of the 34 cities in Gansu. Its position in the ranks since 1975 has fallen; relative to other cities in Gansu, street construction in Gangu has become more connected. Gangu ranked 15th in 1975, 9th in 1976-1990, 28th in 1991-2000 and 22nd in 2001-2014.

Gangu 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 decrease.

How do development practices in Gangu fare in comparison to others in China? Most recently in 2001-2014, street construction in Gangu was the 802nd-most disconnected out of the 1651 cities in China. Its position in the ranks since 1975 has fallen; relative to other cities in China, street construction in Gangu has become more connected. Gangu ranked 496th in 1975, 147th in 1976-1990, 1088th in 1991-2000 and 802nd in 2001-2014.

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

To date, Gangu is the 13th-most disconnected out of the 34 cities in Gansu. Its position in the ranks since 1975 has risen; relative to other cities in Gansu, the street network in Gangu has become more disconnected. Gangu ranked 15th in 1975, 13th in 1976-1990, 13th in 1991-2000 and 13th in 2001-2014.

Gangu and China follow the same trend in the disconnectivity of their aggregate street networks. The SNDi for both of these peaked in 1976-1990.

To date, Gangu is the 296th-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 Gangu has become more disconnected. Gangu ranked 496th in 1975, 257th in 1976-1990, 250th in 1991-2000 and 296th in 2001-2014.

As of 2015, Gangu had a built-up area of 11.14 square kilometers, and a population of 117105 people.

These are some other cities with approximately the same population: