Street-network Sprawl in Abuja, Nigeria

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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:

• nodal degree
• dendricity, the tree-likeness of the street network
• circuity, the ratio of the distance by road to the straight-line distance of two locations on the street network
• sinuosity, the curviness of a street

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:

• Global trends toward urban street-network sprawl
• A global assessment of street-network sprawl

To see the state of street-network sprawl across the globe, visit the sprawlmap.

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Abuja: city in Federal Capital Territory, Nigeria

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 Abuja, Nigeria on the sprawlmap

How have Abuja's street networks changed over time?

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Abuja as of 2014, the overall level of street-network sprawl is 5.16, which is highly disconnected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 4.77, 4.96, 5.06 and 5.29. In each period, new street development in Abuja steadily grows more disconnected than in the last.

Quantity of street network construction: The street network in Abuja spans a total of 3195 kilometers. It is dominated by roads constructed in 2001-2014. These roads have an SNDi of 5.29, 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 4.77, 4.95, 5.02 and 5.16. Overall, the SNDi of the aggregate street network has risen: the street network in Abuja has become more disconnected. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 0.19 points, but between 1991-2000 and 2001-2014, it rose by just 0.14.

Abuja in context: Street-network sprawl of new development

Abuja and Federal Capital Territory do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Abuja rose steadily, while the SNDi of street constructions in Federal Capital Territory was at its lowest in 1976-1990.

How do development practices in Abuja fare in comparison to others in Federal Capital Territory? Most recently in 2001-2014, street construction in Abuja was the 3rd-most disconnected out of the 8 cities in Federal Capital Territory. Its position in the ranks since 1975 has fallen; relative to other cities in Federal Capital Territory, street construction in Abuja has become more connected. Abuja ranked 1st in 1975, 1st in 1976-1990, 2nd in 1991-2000 and 3rd in 2001-2014.

Abuja and Nigeria do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Abuja rose steadily, while the SNDi of street constructions in Nigeria peaked in 1991-2000.

Abuja in context: Aggregate street-network sprawl

Abuja and Federal Capital Territory do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Abuja rose steadily, while the SNDi of street constructions in Federal Capital Territory was at its lowest in 1976-1990.

To date, Abuja is the 2nd-most disconnected out of the 8 cities in Federal Capital Territory. Its position in the ranks since 1975 has fallen; relative to other cities in Federal Capital Territory, the street network in Abuja has become more connected. Abuja ranked 1st in 1975, 1st in 1976-1990, 2nd in 1991-2000 and 2nd in 2001-2014.

Abuja and Nigeria follow the same trend in the disconnectivity of their aggregate street networks. The SNDi for both of these rose steadily.

What about other similarly-populated cities?

As of 2015, Abuja had a built-up area of 135.15 square kilometers, and a population of 1450169 people.

These are some other cities with approximately the same population:

• Liuzhou, China
• Yinchuan, China
• Muzaffarpur, India