Street-network Sprawl in Madagascar

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.

Madagascar

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 Madagascar on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Madagascar as of 2014, the overall level of street-network sprawl is 5.27, which is highly disconnected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 4.96, 4.96, 7.27 and 6.38. Disconnectivity in street construction in Madagascar follows a zig-zag trend. In 1976-1990, street construction was most disconnected, while construction was most connected in 1991-2000.

Quantity of street network construction: The street network in Madagascar spans a total of 24096 kilometers. The period with the greatest volume of street construction was 1976-1990. These roads have an SNDi of 4.96, 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 4.96, 4.97, 5.18 and 5.27. Overall, the SNDi of the aggregate street network has risen: the street network in Madagascar has become more disconnected.

The level of street-network sprawl in new development in Madagascar followed a zig-zag trend with an overall increase. To get a sense of how street development has changed in Madagascar, we can consider three of its most populous regions: Antananarivo, Mahajanga and Fianarantsoa. Out of the three regions, Antananarivo and Mahajanga do not follow the same trend as the country. The level of street-network sprawl in new development in Antananarivo peaked in 1991-2000. The level of street-network sprawl in new development in Mahajanga peaked in 1991-2000.

How do development practices in Madagascar fare in comparison to others in the world? Most recently in 2001-2014, street construction in Madagascar was the 20th-most disconnected out of the 155 countries in the world. Its position in the ranks since 1975 has fallen; relative to other countries in the world, street construction in Madagascar has become more connected. Madagascar ranked 14th in 1975, 26th in 1976-1990, 6th in 1991-2000 and 20th in 2001-2014.

The largest city in Madagascar is Antananarivo, with a population of 2148600 people. Taking into account the entire (i.e. aggregate) street network in Antananarivo as of 2014, the overall level of street-network sprawl is 4.67, which is highly disconnected. The level of street-network sprawl in new development in Antananarivo peaked in 1991-2000.

As of 2014, the city with the most disconnected street network in Madagascar is Antananarivo with an SNDi of 4.67, which is highly disconnected. Conversely, the most connected city is Antanifotsy with an SNDi of 0.95, which is relatively well-connected. See trends for these cities: Antanifotsy, Antananarivo

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

To date, Madagascar is the 15th-most disconnected out of the 155 countries in the world. Its position in the ranks since 1975 has fallen; relative to other countries in the world, the street network in Madagascar has become more connected. Madagascar ranked 14th in 1975, 19th in 1976-1990, 17th in 1991-2000 and 15th in 2001-2014.

The largest city in Madagascar is Antananarivo, with a population of 2148600 people. Taking into account the entire (i.e. aggregate) street network in Antananarivo as of 2014, the overall level of street-network sprawl is 4.67, which is highly disconnected. The level of street-network sprawl in the aggregate network in Antananarivo rose steadily.