Street-network Sprawl in Enugu, Nigeria

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.

Enugu: region in 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 Enugu, Nigeria on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Enugu as of 2014, the overall level of street-network sprawl is 4.7, which is highly disconnected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 4.39, 4.76, 4.65 and 4.59. Street construction in Enugu 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 Enugu spans a total of 5538 kilometers. It is dominated by roads constructed in 2001-2014. These roads have an SNDi of 4.59, 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 4.39, 4.67, 4.67 and 4.7. Disconnectivity in Enugu's street network follows a zig-zag trend. In 1975, the region was most disconnected; while it was most connected in 2001-2014.

The level of street-network sprawl in new development in Enugu peaked in 1976-1990. To get a sense of how street development has changed in Enugu, we can consider three of its most populous cities: Enugu, Nsukka and Umundi. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in new development in Enugu peaked in 1991-2000. The level of street-network sprawl in new development in Nsukka followed a zig-zag trend with an overall increase. The level of street-network sprawl in new development in Umundi followed a zig-zag trend.

How do development practices in Enugu fare in comparison to others in Nigeria? Most recently in 2001-2014, street construction in Enugu was the 13th-most disconnected out of the 37 regions in Nigeria. Its position in the ranks since 1975 has fallen; relative to other regions in Nigeria, street construction in Enugu has become more connected. Enugu ranked 3rd in 1975, 3rd in 1976-1990, 11th in 1991-2000 and 13th in 2001-2014.

As of 2014, the city with the most disconnected street network in Enugu is Enugu with an SNDi of 4.71, which is highly disconnected. Conversely, the most connected city is Agbani with an SNDi of -0.9, which is very well-connected. See trends for these cities: Agbani, Enugu

The level of street-network sprawl in the aggregate network in Enugu followed a zig-zag trend with an overall increase. To get a sense of how the aggregate street network has changed in Enugu, we can consider three of its most populous cities: Enugu, Nsukka and Umundi. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in the aggregate network in Enugu rose steadily. The level of street-network sprawl in the aggregate network in Nsukka was at its lowest in 1976-1990. The level of street-network sprawl in the aggregate network in Umundi peaked in 1976-1990.

To date, Enugu is the 6th-most disconnected out of the 37 regions in Nigeria. Its position in the ranks since 1975 has fallen; relative to other regions in Nigeria, the street network in Enugu has become more connected. Enugu ranked 3rd in 1975, 3rd in 1976-1990, 4th in 1991-2000 and 6th in 2001-2014.