Street-network Sprawl in Garoua-Boulaï, Cameroon

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.

Garoua-Boulaï: city in Est, Cameroon

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 Garoua-Boulaï, Cameroon on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Garoua-Boulaï as of 2014, the overall level of street-network sprawl is 0.92, which is relatively well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 0.04, 0.69, 2.25 and 1.48. Street construction in Garoua-Boulaï 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 Garoua-Boulaï spans a total of 109 kilometers. It is dominated by roads constructed in 1976-1990. These roads have an SNDi of 0.69, 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 0.04, 0.57, 0.68 and 0.92. Overall, the SNDi of the aggregate street network has risen: the street network in Garoua-Boulaï has become more disconnected. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 0.54 points, but between 1991-2000 and 2001-2014, it rose by just 0.24.

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

How do development practices in Garoua-Boulaï fare in comparison to others in Est? Most recently in 2001-2014, street construction in Garoua-Boulaï was the 3rd-most disconnected out of the 4 cities in Est. Its position in the ranks since 1975 has not changed. Garoua-Boulaï ranked 3rd in 1975, 4th in 1976-1990, 4th in 1991-2000 and 3rd in 2001-2014.

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

How do development practices in Garoua-Boulaï fare in comparison to others in Cameroon? Most recently in 2001-2014, street construction in Garoua-Boulaï was the 25th-most disconnected out of the 51 cities in Cameroon. Its position in the ranks since 1975 has risen; relative to other cities in Cameroon, street construction in Garoua-Boulaï has become more disconnected. Garoua-Boulaï ranked 33rd in 1975, 37th in 1976-1990, 30th in 1991-2000 and 25th in 2001-2014.

Garoua-Boulaï and Est follow the same trend in the disconnectivity of their aggregate street networks. The SNDi for both of these rose steadily.

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

Garoua-Boulaï and Cameroon follow the same trend in the disconnectivity of their aggregate street networks. The SNDi for both of these rose steadily.

To date, Garoua-Boulaï is the 38th-most disconnected out of the 51 cities in Cameroon. Its position in the ranks since 1975 has fallen; relative to other cities in Cameroon, the street network in Garoua-Boulaï has become more connected. Garoua-Boulaï ranked 33rd in 1975, 41st in 1976-1990, 39th in 1991-2000 and 38th in 2001-2014.

As of 2015, Garoua-Boulaï had a built-up area of 3.64 square kilometers, and a population of 73697 people.

These are some other cities with approximately the same population: