Street-network Sprawl in Chun'an, 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.

Chun'an: city in Zhejiang, 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 Chun'an, China on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Chun'an as of 2014, the overall level of street-network sprawl is 3.79, which is highly disconnected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 2.97, 2.66, 3.05 and 5.75. The disconnectivity of new streets constructed in Chun'an fell, then rose. In 1976-1990, new street layouts were the most connected.

Quantity of street network construction: The street network in Chun'an spans a total of 158 kilometers. The period with the greatest volume of street construction was 2001-2014. These roads have an SNDi of 5.75, 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 2.97, 2.77, 2.85 and 3.79. The SNDi of the aggregate street network in fell at first, but Chun'an has worsened in disconnectivity since 1990.

Chun'an and Zhejiang do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Chun'an was at its lowest in 1976-1990, while the SNDi of street constructions in Zhejiang peaked in 1976-1990.

How do development practices in Chun'an fare in comparison to others in Zhejiang? Most recently in 2001-2014, street construction in Chun'an was the 3rd-most disconnected out of the 94 cities in Zhejiang. Its position in the ranks since 1975 has risen; relative to other cities in Zhejiang, street construction in Chun'an has become more disconnected. Chun'an ranked 18th in 1975, 22nd in 1976-1990, 9th in 1991-2000 and 3rd in 2001-2014.

Chun'an and China do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Chun'an was at its lowest in 1976-1990, while the SNDi of street constructions in China followed a zig-zag trend with an overall decrease.

How do development practices in Chun'an fare in comparison to others in China? Most recently in 2001-2014, street construction in Chun'an was the 58th-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 Chun'an has become more disconnected. Chun'an ranked 253rd in 1975, 407th in 1976-1990, 238th in 1991-2000 and 58th in 2001-2014.

Chun'an and Zhejiang do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Chun'an was at its lowest in 1976-1990, while the SNDi of street constructions in Zhejiang peaked in 1976-1990.

To date, Chun'an is the 7th-most disconnected out of the 94 cities in Zhejiang. Its position in the ranks since 1975 has risen; relative to other cities in Zhejiang, the street network in Chun'an has become more disconnected. Chun'an ranked 18th in 1975, 18th in 1976-1990, 13th in 1991-2000 and 7th in 2001-2014.

Chun'an and China do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Chun'an was at its lowest in 1976-1990, while the SNDi of street constructions in China peaked in 1976-1990.

To date, Chun'an is the 130th-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 Chun'an has become more disconnected. Chun'an ranked 253rd in 1975, 359th in 1976-1990, 316th in 1991-2000 and 130th in 2001-2014.

As of 2015, Chun'an had a built-up area of 9.35 square kilometers, and a population of 106638 people.

These are some other cities with approximately the same population: