Street-network Sprawl in Faranah, Guinea

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.

Faranah: region in Guinea

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 Faranah, Guinea on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Faranah as of 2014, the overall level of street-network sprawl is 4.38, which is highly disconnected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 2.54, 5.03, 4.06 and 5.53. Disconnectivity in street construction in Faranah follows a zig-zag trend. In 1975, street construction was most disconnected, while construction was most connected in 2001-2014.

Quantity of street network construction: The street network in Faranah spans a total of 3229 kilometers. The period with the greatest volume of street construction was 1991-2000. These roads have an SNDi of 4.06, 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 2.54, 3.96, 4.04 and 4.38. Overall, the SNDi of the aggregate street network has risen: the street network in Faranah has become more disconnected. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 1.42 points, but between 1991-2000 and 2001-2014, it rose by just 0.34.

The level of street-network sprawl in new development in Faranah followed a zig-zag trend with an overall increase. To get a sense of how street development has changed in Faranah, we can consider three of its most populous cities: Kissidougou, Faranah and Dinguiraye. Out of the three cities, Dinguiraye does not follow the same trend as the region. The level of street-network sprawl in new development in Dinguiraye followed a zig-zag trend with an overall decrease.

How do development practices in Faranah fare in comparison to others in Guinea? Most recently in 2001-2014, street construction in Faranah was the 4th-most disconnected out of the 8 regions in Guinea. Its position in the ranks since 1975 has not changed. Faranah ranked 4th in 1975, 2nd in 1976-1990, 3rd in 1991-2000 and 4th in 2001-2014.

As of 2014, the city with the most disconnected street network in Faranah is Faranah with an SNDi of 3.01, which is in the 40th to 60th percentile of disconnectedness. Conversely, the most connected city is Dinguiraye with an SNDi of -0.63, which is very well-connected. See trends for these cities: Dinguiraye, Faranah

The level of street-network sprawl in the aggregate network in Faranah rose steadily. To get a sense of how the aggregate street network has changed in Faranah, we can consider three of its most populous cities: Kissidougou, Faranah and Dinguiraye. Out of the three cities, Kissidougou and Dinguiraye do not follow the same trend as the region. The level of street-network sprawl in the aggregate network in Kissidougou followed a zig-zag trend with an overall increase. The level of street-network sprawl in the aggregate network in Dinguiraye fell steadily.

To date, Faranah is the 4th-most disconnected out of the 8 regions in Guinea. Its position in the ranks since 1975 has not changed. Faranah ranked 4th in 1975, 3rd in 1976-1990, 3rd in 1991-2000 and 4th in 2001-2014.