Street-network Sprawl in Muchinga, 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.

Muchinga: 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 Muchinga, Zambia on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Muchinga as of 2014, the overall level of street-network sprawl is 4.14, which is highly disconnected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 2.97, 4.9, 4.24 and 4.14. Street construction in Muchinga increased in disconnectivity initially but has since improved. The streets constructed in 1976-1990 were the most disconnected.

Quantity of street network construction: The street network in Muchinga spans a total of 1823 kilometers. It is dominated by roads constructed in 2001-2014. These roads have an SNDi of 4.14, 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, 4.11, 4.19 and 4.14. The aggregate street network in Muchinga increased in disconnectivity initially,but the trend has turned around after 2000.

The level of street-network sprawl in new development in Muchinga peaked in 1976-1990. To get a sense of how street development has changed in Muchinga, we can consider three of its most populous cities: Tunduma, Isoka and Chinsali. Out of the three cities, Isoka and Chinsali do not follow the same trend as the region. The level of street-network sprawl in new development in Isoka followed a zig-zag trend with an overall increase. The level of street-network sprawl in new development in Chinsali rose steadily.

How do development practices in Muchinga fare in comparison to others in Zambia? Most recently in 2001-2014, street construction in Muchinga was the 4th-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 Muchinga has become more connected. Muchinga ranked 3rd in 1975, 1st in 1976-1990, 4th in 1991-2000 and 4th in 2001-2014.

As of 2014, the city with the most disconnected street network in Muchinga is Chinsali with an SNDi of 3.91, which is highly disconnected. Conversely, the most connected city is Isoka with an SNDi of 1.31, which is relatively well-connected. See trends for these cities: Isoka, Chinsali

The level of street-network sprawl in the aggregate network in Muchinga peaked in 1991-2000. To get a sense of how the aggregate street network has changed in Muchinga, we can consider three of its most populous cities: Tunduma, Isoka and Chinsali. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in the aggregate network in Tunduma peaked in 1976-1990. The level of street-network sprawl in the aggregate network in Isoka was at its lowest in 1976-1990. The level of street-network sprawl in the aggregate network in Chinsali rose steadily.

To date, Muchinga is the 1st-most disconnected out of the 10 regions in Zambia. Its position in the ranks since 1975 has risen; relative to other regions in Zambia, the street network in Muchinga has become more disconnected. Muchinga ranked 3rd in 1975, 1st in 1976-1990, 1st in 1991-2000 and 1st in 2001-2014.