Street-network Sprawl in Tunduma, 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.

Tunduma: city in Muchinga, 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 Tunduma, Zambia on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Tunduma as of 2014, the overall level of street-network sprawl is 2.88, 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 3.43, 4.46, 2.59 and 2.53. Street construction in Tunduma 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 Tunduma spans a total of 164 kilometers. It is dominated by roads constructed in 2001-2014. These roads have an SNDi of 2.53, 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 3.43, 3.91, 3.19 and 2.88. The aggregate street network in Tunduma increased in disconnectivity initially,but the trend has turned around after 1990.

Tunduma and Muchinga follow the same trend in the disconnectivity of their street network constructions. The SNDi for both of these peaked in 1976-1990.

How do development practices in Tunduma fare in comparison to others in Muchinga? Most recently in 2001-2014, street construction in Tunduma was the 2nd-most disconnected out of the 3 cities in Muchinga. Its position in the ranks since 1975 has fallen; relative to other cities in Muchinga, street construction in Tunduma has become more connected. Tunduma ranked 1st in 1975, 1st in 1976-1990, 3rd in 1991-2000 and 2nd in 2001-2014.

Tunduma and Zambia do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Tunduma peaked in 1976-1990, while the SNDi of street constructions in Zambia rose steadily.

How do development practices in Tunduma fare in comparison to others in Zambia? Most recently in 2001-2014, street construction in Tunduma was the 18th-most disconnected out of the 38 cities in Zambia. Its position in the ranks since 1975 has fallen; relative to other cities in Zambia, street construction in Tunduma has become more connected. Tunduma ranked 6th in 1975, 3rd in 1976-1990, 11th in 1991-2000 and 18th in 2001-2014.

Tunduma and Muchinga do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Tunduma peaked in 1976-1990, while the SNDi of street constructions in Muchinga peaked in 1991-2000.

To date, Tunduma is the 2nd-most disconnected out of the 3 cities in Muchinga. Its position in the ranks since 1975 has fallen; relative to other cities in Muchinga, the street network in Tunduma has become more connected. Tunduma ranked 1st in 1975, 1st in 1976-1990, 2nd in 1991-2000 and 2nd in 2001-2014.

Tunduma and Zambia do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Tunduma peaked in 1976-1990, while the SNDi of street constructions in Zambia rose steadily.

To date, Tunduma is the 10th-most disconnected out of the 38 cities in Zambia. Its position in the ranks since 1975 has fallen; relative to other cities in Zambia, the street network in Tunduma has become more connected. Tunduma ranked 6th in 1975, 4th in 1976-1990, 7th in 1991-2000 and 10th in 2001-2014.

As of 2015, Tunduma had a built-up area of 8.84 square kilometers, and a population of 256475 people.

These are some other cities with approximately the same population: