Street-network Sprawl in Western, Zambia

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.

Western: region in Zambia

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 Western, Zambia on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Western as of 2014, the overall level of street-network sprawl is 2.41, 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 2.07, 2.25, 2.08 and 2.87. Disconnectivity in street construction in Western follows a zig-zag trend. In 1975, street construction was most disconnected, while construction was most connected in 2001-2014.

Quantity of street network construction: The street network in Western spans a total of 3676 kilometers. The period with the greatest volume of street construction was 2001-2014. These roads have an SNDi of 2.87, which is in the 40th to 60th percentile of disconnectedness.

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 2.07, 2.21, 2.19 and 2.41. Disconnectivity in Western's street network follows a zig-zag trend. In 1975, the region was most disconnected; while it was most connected in 2001-2014.

The level of street-network sprawl in new development in Western followed a zig-zag trend with an overall increase. To get a sense of how street development has changed in Western, we can consider two of its most populous cities: Mongu and Kaoma. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in new development in Mongu peaked in 1991-2000. The level of street-network sprawl in new development in Kaoma followed a zig-zag trend.

How do development practices in Western fare in comparison to others in Zambia? Most recently in 2001-2014, street construction in Western was the 10th-most disconnected out of the 10 regions in Zambia. Its position in the ranks since 1975 has fallen; relative to other regions in Zambia, street construction in Western has become more connected. Western ranked 7th in 1975, 9th in 1976-1990, 10th in 1991-2000 and 10th in 2001-2014.

As of 2014, the city with the most disconnected street network in Western is Mongu with an SNDi of 1.24, which is relatively well-connected. Conversely, the most connected city is Kaoma with an SNDi of 0.59, which is relatively well-connected. See trends for these cities: Kaoma, Mongu

The level of street-network sprawl in the aggregate network in Western followed a zig-zag trend with an overall increase. To get a sense of how the aggregate street network has changed in Western, we can consider two of its most populous cities: Mongu and Kaoma. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in the aggregate network in Mongu peaked in 1991-2000. The level of street-network sprawl in the aggregate network in Kaoma followed a zig-zag trend.

To date, Western is the 9th-most disconnected out of the 10 regions in Zambia. Its position in the ranks since 1975 has fallen; relative to other regions in Zambia, the street network in Western has become more connected. Western ranked 7th in 1975, 6th in 1976-1990, 9th in 1991-2000 and 9th in 2001-2014.