Street-network Sprawl in Quảng Ngãi, Vietnam

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.

Quảng Ngãi: region in Vietnam

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 Quảng Ngãi, Vietnam on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Quảng Ngãi as of 2014, the overall level of street-network sprawl is 4.5, which is highly disconnected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 4.09, 4.35, 4.59 and 4.95. In each period, new street development in Quảng Ngãi steadily grows more disconnected than in the last.

Quantity of street network construction: The street network in Quảng Ngãi spans a total of 3967 kilometers. The period with the greatest volume of street construction was 1976-1990. These roads have an SNDi of 4.35, 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 4.09, 4.23, 4.41 and 4.5. Overall, the SNDi of the aggregate street network has risen: the street network in Quảng Ngãi has become more disconnected. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 0.14 points, but between 1991-2000 and 2001-2014, it rose by just 0.09.

The level of street-network sprawl in new development in Quảng Ngãi rose steadily. To get a sense of how street development has changed in Quảng Ngãi, we can consider two of its most populous cities: Quảng Ngãi and Vĩnh An. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in new development in Quảng Ngãi was at its lowest in 1976-1990. The level of street-network sprawl in new development in Vĩnh An followed a zig-zag trend with an overall decrease.

How do development practices in Quảng Ngãi fare in comparison to others in Vietnam? Most recently in 2001-2014, street construction in Quảng Ngãi was the 8th-most disconnected out of the 59 regions in Vietnam. Its position in the ranks since 1975 has risen; relative to other regions in Vietnam, street construction in Quảng Ngãi has become more disconnected. Quảng Ngãi ranked 10th in 1975, 10th in 1976-1990, 9th in 1991-2000 and 8th in 2001-2014.

As of 2014, the city with the most disconnected street network in Quảng Ngãi is Vĩnh An with an SNDi of 5.0, which is highly disconnected. Conversely, the most connected city is Quảng Ngãi with an SNDi of 4.55, which is highly disconnected. See trends for these cities: Quảng Ngãi, Vĩnh An

The level of street-network sprawl in the aggregate network in Quảng Ngãi rose steadily. To get a sense of how the aggregate street network has changed in Quảng Ngãi, we can consider two of its most populous cities: Quảng Ngãi and Vĩnh An. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in the aggregate network in Quảng Ngãi was at its lowest in 1976-1990. The level of street-network sprawl in the aggregate network in Vĩnh An followed a zig-zag trend with an overall decrease.

To date, Quảng Ngãi is the 8th-most disconnected out of the 59 regions in Vietnam. Its position in the ranks since 1975 has risen; relative to other regions in Vietnam, the street network in Quảng Ngãi has become more disconnected. Quảng Ngãi ranked 10th in 1975, 10th in 1976-1990, 7th in 1991-2000 and 8th in 2001-2014.