Street-network Sprawl in Southern, Botswana

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.

Southern: region in Botswana

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 Southern, Botswana on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Southern as of 2014, the overall level of street-network sprawl is 2.6, 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 0.86, 2.55, 2.9 and 2.4. Street construction in Southern 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 Southern spans a total of 1947 kilometers. It is dominated by roads constructed in 2001-2014. These roads have an SNDi of 2.4, 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 0.86, 2.5, 2.69 and 2.6. The aggregate street network in Southern increased in disconnectivity initially,but the trend has turned around after 2000.

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

How do development practices in Southern fare in comparison to others in Botswana? Most recently in 2001-2014, street construction in Southern was the 6th-most disconnected out of the 7 regions in Botswana. Its position in the ranks since 1975 has risen; relative to other regions in Botswana, street construction in Southern has become more disconnected. Southern ranked 7th in 1975, 4th in 1976-1990, 4th in 1991-2000 and 6th in 2001-2014.

As of 2014, the city with the most disconnected street network in Southern is Kanye with an SNDi of 2.58, which is in the 40th to 60th percentile of disconnectedness. Conversely, the most connected city is Kanye with an SNDi of 2.58, which is in the 40th to 60th percentile of disconnectedness. See trends for these cities: Kanye, Kanye

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

To date, Southern is the 5th-most disconnected out of the 7 regions in Botswana. Its position in the ranks since 1975 has risen; relative to other regions in Botswana, the street network in Southern has become more disconnected. Southern ranked 7th in 1975, 4th in 1976-1990, 4th in 1991-2000 and 5th in 2001-2014.