Street-network Sprawl in Idiroko, 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.

Idiroko: city in Ogun, 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 Idiroko, Nigeria on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Idiroko as of 2014, the overall level of street-network sprawl is 3.19, 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 -0.23, 3.52, 4.16 and 0.92. Street construction in Idiroko 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 Idiroko spans a total of 41 kilometers. It is dominated by roads constructed in 1976-1990. These roads have an SNDi of 3.52, 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 -0.23, 3.45, 3.68 and 3.19. The aggregate street network in Idiroko increased in disconnectivity initially,but the trend has turned around after 2000.

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

How do development practices in Idiroko fare in comparison to others in Ogun? Most recently in 2001-2014, street construction in Idiroko was the 13th-most disconnected out of the 13 cities in Ogun. Its position in the ranks since 1975 has fallen; relative to other cities in Ogun, street construction in Idiroko has become more connected. Idiroko ranked 11th in 1975, 6th in 1976-1990, 4th in 1991-2000 and 13th in 2001-2014.

Idiroko and Nigeria follow the same trend in the disconnectivity of their street network constructions. The SNDi for both of these peaked in 1991-2000.

How do development practices in Idiroko fare in comparison to others in Nigeria? Most recently in 2001-2014, street construction in Idiroko was the 293rd-most disconnected out of the 411 cities in Nigeria. Its position in the ranks since 1975 has fallen; relative to other cities in Nigeria, street construction in Idiroko has become more connected. Idiroko ranked 212th in 1975, 72nd in 1976-1990, 81st in 1991-2000 and 293rd in 2001-2014.

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

To date, Idiroko is the 6th-most disconnected out of the 13 cities in Ogun. Its position in the ranks since 1975 has risen; relative to other cities in Ogun, the street network in Idiroko has become more disconnected. Idiroko ranked 11th in 1975, 4th in 1976-1990, 4th in 1991-2000 and 6th in 2001-2014.

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

To date, Idiroko is the 120th-most disconnected out of the 411 cities in Nigeria. Its position in the ranks since 1975 has risen; relative to other cities in Nigeria, the street network in Idiroko has become more disconnected. Idiroko ranked 212th in 1975, 50th in 1976-1990, 54th in 1991-2000 and 120th in 2001-2014.

As of 2015, Idiroko had a built-up area of 5.82 square kilometers, and a population of 86223 people.

These are some other cities with approximately the same population: