Street-network Sprawl in Al Hudaydah, 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.

Al Hudaydah: region in 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 Al Hudaydah, Yemen on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Al Hudaydah as of 2014, the overall level of street-network sprawl is 2.23, which is relatively well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 3.19, 4.06, nan and 2.21. Data was not available in 1991-2000.

Quantity of street network construction: The street network in Al Hudaydah spans a total of 3231 kilometers. It is dominated by roads constructed in 2001-2014. These roads have an SNDi of 2.21, 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 3.19, 4.08, 3.86 and 2.23. The aggregate street network in Al Hudaydah increased in disconnectivity initially,but the trend has turned around after 1990.

The level of street-network sprawl in new development in Al Hudaydah followed a zig-zag trend with an overall decrease. To get a sense of how street development has changed in Al Hudaydah, we can consider two of its most populous cities: Hodeidah and Al Jarrahi. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in new development in Hodeidah followed a zig-zag trend. The level of street-network sprawl in new development in Al Jarrahi followed a zig-zag trend.

How do development practices in Al Hudaydah fare in comparison to others in Yemen? Most recently in 2001-2014, street construction in Al Hudaydah was the 15th-most disconnected out of the 16 regions in Yemen. Its position in the ranks since 1975 has risen; relative to other regions in Yemen, street construction in Al Hudaydah has become more disconnected. Al Hudaydah ranked 12th in 1975, 6th in 1976-1990 and 15th in 2001-2014. There was no ranking in 1991-2000 due to unavailable data.

As of 2014, the city with the most disconnected street network in Al Hudaydah is Hodeidah with an SNDi of 1.22, which is relatively well-connected. Conversely, the most connected city is Al Jarrahi with an SNDi of -0.11, which is very well-connected. See trends for these cities: Al Jarrahi, Hodeidah

The level of street-network sprawl in the aggregate network in Al Hudaydah peaked in 1976-1990. To get a sense of how the aggregate street network has changed in Al Hudaydah, we can consider two of its most populous cities: Hodeidah and Al Jarrahi. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in the aggregate network in Hodeidah followed a zig-zag trend. The level of street-network sprawl in the aggregate network in Al Jarrahi followed a zig-zag trend.

To date, Al Hudaydah is the 14th-most disconnected out of the 16 regions in Yemen. Its position in the ranks since 1975 has fallen; relative to other regions in Yemen, the street network in Al Hudaydah has become more connected. Al Hudaydah ranked 12th in 1975, 11th in 1976-1990, 12th in 1991-2000 and 14th in 2001-2014.