Street-network Sprawl in Sana'a, Yemen

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.

Sana'a: city in Amanat Al Asimah, Yemen

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 Sana'a, Yemen on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Sana'a as of 2014, the overall level of street-network sprawl is 1.33, which is relatively well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 0.96, 1.12, 2.73 and 2.55. Street construction in Sana'a 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 Sana'a spans a total of 2169 kilometers. It is dominated by roads constructed in 1976-1990. These roads have an SNDi of 1.12, 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 0.96, 1.09, 1.17 and 1.33. Overall, the SNDi of the aggregate street network has risen: the street network in Sana'a has become more disconnected.

Sana'a and Amanat Al Asimah do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Sana'a peaked in 1991-2000, while the SNDi of street constructions in Amanat Al Asimah rose steadily.

How do development practices in Sana'a fare in comparison to others in Amanat Al Asimah? Most recently in 2001-2014, street construction in Sana'a was the 1st-most disconnected out of the 1 cities in Amanat Al Asimah. Its position in the ranks since 1975 has not changed. Sana'a ranked 1st in 1975, 1st in 1976-1990, 1st in 1991-2000 and 1st in 2001-2014.

Sana'a and Yemen do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Sana'a peaked in 1991-2000, while the SNDi of street constructions in Yemen followed a zig-zag trend with an overall decrease.

How do development practices in Sana'a fare in comparison to others in Yemen? Most recently in 2001-2014, street construction in Sana'a was the 15th-most disconnected out of the 36 cities in Yemen. Its position in the ranks since 1975 has fallen; relative to other cities in Yemen, street construction in Sana'a has become more connected. Sana'a ranked 11th in 1975, 17th in 1976-1990, 9th in 1991-2000 and 15th in 2001-2014.

Sana'a and Amanat Al Asimah follow the same trend in the disconnectivity of their aggregate street networks. The SNDi for both of these rose steadily.

To date, Sana'a is the 1st-most disconnected out of the 1 cities in Amanat Al Asimah. Its position in the ranks since 1975 has not changed. Sana'a ranked 1st in 1975, 1st in 1976-1990, 1st in 1991-2000 and 1st in 2001-2014.

Sana'a and Yemen do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Sana'a rose steadily, while the SNDi of street constructions in Yemen was at its lowest in 1976-1990.

To date, Sana'a is the 29th-most disconnected out of the 36 cities in Yemen. Its position in the ranks since 1975 has fallen; relative to other cities in Yemen, the street network in Sana'a has become more connected. Sana'a ranked 11th in 1975, 17th in 1976-1990, 20th in 1991-2000 and 29th in 2001-2014.

As of 2015, Sana'a had a built-up area of 47.85 square kilometers, and a population of 2537059 people.

These are some other cities with approximately the same population: