Street-network Sprawl in Yucheng, China

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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:

• nodal degree
• dendricity, the tree-likeness of the street network
• circuity, the ratio of the distance by road to the straight-line distance of two locations on the street network
• sinuosity, the curviness of a street

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:

• Global trends toward urban street-network sprawl
• A global assessment of street-network sprawl

To see the state of street-network sprawl across the globe, visit the sprawlmap.

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Yucheng: city in Henan, 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 Yucheng, China on the sprawlmap

How have Yucheng's street networks changed over time?

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Yucheng as of 2014, the overall level of street-network sprawl is -0.61, which is very well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are -0.73, -0.47, -0.44 and -0.76. Street construction in Yucheng increased in disconnectivity initially but has since improved. The streets constructed in 1991-2000 were the most disconnected.

Quantity of street network construction: The street network in Yucheng spans a total of 111 kilometers. It is dominated by roads constructed in 2001-2014. These roads have an SNDi of -0.76, which is very 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 -0.73, -0.59, -0.6 and -0.61. The aggregate street network in Yucheng increased in disconnectivity initially,but the trend has turned around after 1990.

Yucheng in context: Street-network sprawl of new development

Yucheng and Henan follow the same trend in the disconnectivity of their street network constructions. The SNDi for both of these peaked in 1991-2000.

How do development practices in Yucheng fare in comparison to others in Henan? Most recently in 2001-2014, street construction in Yucheng was the 106th-most disconnected out of the 118 cities in Henan. Its position in the ranks since 1975 has fallen; relative to other cities in Henan, street construction in Yucheng has become more connected. Yucheng ranked 64th in 1975, 107th in 1976-1990, 87th in 1991-2000 and 106th in 2001-2014.

Yucheng and China do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Yucheng peaked in 1991-2000, while the SNDi of street constructions in China followed a zig-zag trend with an overall decrease.

Yucheng in context: Aggregate street-network sprawl

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

To date, Yucheng is the 115th-most disconnected out of the 118 cities in Henan. Its position in the ranks since 1975 has fallen; relative to other cities in Henan, the street network in Yucheng has become more connected. Yucheng ranked 64th in 1975, 109th in 1976-1990, 113th in 1991-2000 and 115th in 2001-2014.

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

What about other similarly-populated cities?

As of 2015, Yucheng had a built-up area of 15.75 square kilometers, and a population of 70290 people.

These are some other cities with approximately the same population:

• Sidorejo, Indonesia
• Ratu, India
• Ye, China

For some related information about population, urban extent and density, and roads, visit the Atlas of Urban Expansion.