Street-network Sprawl in Gambia

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.

Gambia

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 Gambia on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Gambia as of 2014, the overall level of street-network sprawl is 1.45, which is relatively well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 0.55, 1.66, 1.72 and 2.66. In each period, new street development in Gambia steadily grows more disconnected than in the last. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 1.11 points, but between 1991-2000 and 2001-2014, it rose by just 0.94.

Quantity of street network construction: The street network in Gambia spans a total of 6999 kilometers. The period with the greatest volume of street construction was 1991-2000. These roads have an SNDi of 1.72, 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 0.55, 1.16, 1.32 and 1.45. Overall, the SNDi of the aggregate street network has risen: the street network in Gambia has become more disconnected. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 0.61 points, but between 1991-2000 and 2001-2014, it rose by just 0.13.

The level of street-network sprawl in new development in Gambia rose steadily. To get a sense of how street development has changed in Gambia, we can consider two of its most populous regions: Western and North Bank. Out of the two regions, North Bank does not follow the same trend as the country. The level of street-network sprawl in new development in North Bank was at its lowest in 1976-1990.

How do development practices in Gambia fare in comparison to others in the world? Most recently in 2001-2014, street construction in Gambia was the 138th-most disconnected out of the 155 countries in the world. Its position in the ranks since 1975 has risen; relative to other countries in the world, street construction in Gambia has become more disconnected. Gambia ranked 153rd in 1975, 136th in 1976-1990, 151st in 1991-2000 and 138th in 2001-2014.

The largest city in Gambia is Serrekunda, with a population of 727900 people. Taking into account the entire (i.e. aggregate) street network in Serrekunda as of 2014, the overall level of street-network sprawl is 0.8, which is relatively well-connected. The level of street-network sprawl in new development in Serrekunda rose steadily.

As of 2014, the city with the most disconnected street network in Gambia is Serrekunda with an SNDi of 0.8, which is relatively well-connected. Conversely, the most connected city is Brikama with an SNDi of -0.06, which is very well-connected. See trends for these cities: Brikama, Serrekunda

The level of street-network sprawl in the aggregate network in Gambia rose steadily. To get a sense of how the aggregate street network has changed in Gambia, we can consider two of its most populous regions: Western and North Bank. Out of the two regions, North Bank does not follow the same trend as the country. The level of street-network sprawl in the aggregate network in North Bank was at its lowest in 1976-1990.

To date, Gambia is the 151st-most disconnected out of the 155 countries in the world. Its position in the ranks since 1975 has risen; relative to other countries in the world, the street network in Gambia has become more disconnected. Gambia ranked 153rd in 1975, 151st in 1976-1990, 151st in 1991-2000 and 151st in 2001-2014.

The largest city in Gambia is Serrekunda, with a population of 727900 people. Taking into account the entire (i.e. aggregate) street network in Serrekunda as of 2014, the overall level of street-network sprawl is 0.8, which is relatively well-connected. The level of street-network sprawl in the aggregate network in Serrekunda rose steadily.