Street-network Sprawl in Daru, Sierra Leone

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.

Daru: city in Eastern, Sierra Leone

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 Daru, Sierra Leone on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Daru as of 2014, the overall level of street-network sprawl is 3.04, 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 2.43, nan, 4.02 and 4.72. Data was not available in 1976-1990.

Quantity of street network construction: The street network in Daru spans a total of 29 kilometers. It is dominated by roads constructed prior to 1975. These roads have an SNDi of 2.43, 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 2.43, 2.43, 2.99 and 3.04. Overall, the SNDi of the aggregate street network has risen: the street network in Daru has become more disconnected.

Daru and Eastern do not follow the same trend in the disconnectivity of their street network constructions. There was not enough data from the city, while the SNDi of street constructions in Eastern peaked in 1976-1990.

How do development practices in Daru fare in comparison to others in Eastern? Most recently in 2001-2014, street construction in Daru was the 2nd-most disconnected out of the 3 cities in Eastern. Its position in the ranks since 1975 has risen; relative to other cities in Eastern, street construction in Daru has become more disconnected. Daru ranked 3rd in 1975, 3rd in 1991-2000 and 2nd in 2001-2014. There was no ranking in 1976-1990 due to unavailable data.

Daru and Sierra Leone do not follow the same trend in the disconnectivity of their street network constructions. There was not enough data from the city, while the SNDi of street constructions in Sierra Leone followed a zig-zag trend with an overall increase.

How do development practices in Daru fare in comparison to others in Sierra Leone? Most recently in 2001-2014, street construction in Daru was the 7th-most disconnected out of the 9 cities in Sierra Leone. Its position in the ranks since 1975 has risen; relative to other cities in Sierra Leone, street construction in Daru has become more disconnected. Daru ranked 7th in 1975, 8th in 1991-2000 and 7th in 2001-2014. There was no ranking in 1976-1990 due to unavailable data.

Daru and Eastern do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Daru rose steadily, while the SNDi of street constructions in Eastern rose steadily.

To date, Daru is the 3rd-most disconnected out of the 3 cities in Eastern. Its position in the ranks since 1975 has not changed. Daru ranked 3rd in 1975, 3rd in 1976-1990, 3rd in 1991-2000 and 3rd in 2001-2014.

Daru and Sierra Leone do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Daru rose steadily, while the SNDi of street constructions in Sierra Leone rose steadily.

To date, Daru is the 8th-most disconnected out of the 9 cities in Sierra Leone. Its position in the ranks since 1975 has fallen; relative to other cities in Sierra Leone, the street network in Daru has become more connected. Daru ranked 7th in 1975, 8th in 1976-1990, 8th in 1991-2000 and 8th in 2001-2014.

As of 2015, Daru had a built-up area of 0.33 square kilometers, and a population of 51813 people.

These are some other cities with approximately the same population: