Street-network Sprawl in Mile 91, 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.

Mile 91: city in Northern, 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 Mile 91, Sierra Leone on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Mile 91 as of 2014, the overall level of street-network sprawl is 1.26, which is relatively well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are -0.11, 1.95, 5.28 and -1.17. Street construction in Mile 91 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 Mile 91 spans a total of 21 kilometers. The period with the greatest volume of street construction was 1976-1990. These roads have an SNDi of 1.95, which is relatively well-connected.

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 -0.11, 0.65, 1.42 and 1.26. The aggregate street network in Mile 91 increased in disconnectivity initially,but the trend has turned around after 2000.

Mile 91 and Northern do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Mile 91 peaked in 1991-2000, while the SNDi of street constructions in Northern peaked in 1976-1990.

How do development practices in Mile 91 fare in comparison to others in Northern? Most recently in 2001-2014, street construction in Mile 91 was the 3rd-most disconnected out of the 3 cities in Northern. Its position in the ranks since 1975 has not changed. Mile 91 ranked 3rd in 1975, 3rd in 1976-1990, 3rd in 1991-2000 and 3rd in 2001-2014.

Mile 91 and Sierra Leone do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Mile 91 peaked in 1991-2000, while the SNDi of street constructions in Sierra Leone followed a zig-zag trend with an overall increase.

How do development practices in Mile 91 fare in comparison to others in Sierra Leone? Most recently in 2001-2014, street construction in Mile 91 was the 9th-most disconnected out of the 9 cities in Sierra Leone. Its position in the ranks since 1975 has not changed. Mile 91 ranked 9th in 1975, 7th in 1976-1990, 6th in 1991-2000 and 9th in 2001-2014.

Mile 91 and Northern do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Mile 91 peaked in 1991-2000, while the SNDi of street constructions in Northern rose steadily.

To date, Mile 91 is the 3rd-most disconnected out of the 3 cities in Northern. Its position in the ranks since 1975 has not changed. Mile 91 ranked 3rd in 1975, 3rd in 1976-1990, 3rd in 1991-2000 and 3rd in 2001-2014.

Mile 91 and Sierra Leone do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Mile 91 peaked in 1991-2000, while the SNDi of street constructions in Sierra Leone rose steadily.

To date, Mile 91 is the 9th-most disconnected out of the 9 cities in Sierra Leone. Its position in the ranks since 1975 has not changed. Mile 91 ranked 9th in 1975, 9th in 1976-1990, 9th in 1991-2000 and 9th in 2001-2014.

As of 2015, Mile 91 had a built-up area of 1.45 square kilometers, and a population of 55236 people.

These are some other cities with approximately the same population: