Street-network Sprawl in Zaire, Angola

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.

Zaire: region in Angola

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 Zaire, Angola on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Zaire as of 2014, the overall level of street-network sprawl is 5.25, which is highly disconnected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 4.38, 3.92, 5.31 and 5.73. The disconnectivity of new streets constructed in Zaire fell, then rose. In 1976-1990, new street layouts were the most connected.

Quantity of street network construction: The street network in Zaire spans a total of 3008 kilometers. The period with the greatest volume of street construction was 2001-2014. These roads have an SNDi of 5.73, 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 4.38, 4.32, 4.63 and 5.25. The SNDi of the aggregate street network in fell at first, but Zaire has worsened in disconnectivity since 1990.

The level of street-network sprawl in new development in Zaire was at its lowest in 1976-1990. To get a sense of how street development has changed in Zaire, we can consider two of its most populous cities: M'banza Congo and Soyo. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in new development in M'banza Congo peaked in 1991-2000. The level of street-network sprawl in new development in Soyo followed a zig-zag trend.

How do development practices in Zaire fare in comparison to others in Angola? Most recently in 2001-2014, street construction in Zaire was the 2nd-most disconnected out of the 18 regions in Angola. Its position in the ranks since 1975 has risen; relative to other regions in Angola, street construction in Zaire has become more disconnected. Zaire ranked 3rd in 1975, 6th in 1976-1990, 3rd in 1991-2000 and 2nd in 2001-2014.

As of 2014, the city with the most disconnected street network in Zaire is M'banza Congo with an SNDi of 6.9, which is highly disconnected. Conversely, the most connected city is Soyo with an SNDi of 2.52, which is in the 40th to 60th percentile of disconnectedness. See trends for these cities: Soyo, M'banza Congo

The level of street-network sprawl in the aggregate network in Zaire was at its lowest in 1976-1990. To get a sense of how the aggregate street network has changed in Zaire, we can consider two of its most populous cities: M'banza Congo and Soyo. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in the aggregate network in M'banza Congo peaked in 1991-2000. The level of street-network sprawl in the aggregate network in Soyo rose steadily.

To date, Zaire is the 1st-most disconnected out of the 18 regions in Angola. Its position in the ranks since 1975 has risen; relative to other regions in Angola, the street network in Zaire has become more disconnected. Zaire ranked 3rd in 1975, 4th in 1976-1990, 2nd in 1991-2000 and 1st in 2001-2014.