Street-network Sprawl in Sala ad-Din, Iraq

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.

Sala ad-Din: region in Iraq

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 Sala ad-Din, Iraq on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Sala ad-Din as of 2014, the overall level of street-network sprawl is 2.2, which is relatively well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 1.28, 1.86, 3.16 and 2.64. Street construction in Sala ad-Din 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 Sala ad-Din spans a total of 5690 kilometers. It is dominated by roads constructed in 1976-1990. These roads have an SNDi of 1.86, 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 1.28, 1.85, 1.92 and 2.2. Overall, the SNDi of the aggregate street network has risen: the street network in Sala ad-Din has become more disconnected. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 0.57 points, but between 1991-2000 and 2001-2014, it rose by just 0.28.

The level of street-network sprawl in new development in Sala ad-Din peaked in 1991-2000. To get a sense of how street development has changed in Sala ad-Din, we can consider three of its most populous cities: At Tarimiyah, Hamdi al Bajaji and Tuz Khormato. Out of the three cities, At Tarimiyah and Tuz Khormato do not follow the same trend as the region. The level of street-network sprawl in new development in At Tarimiyah was at its lowest in 1976-1990. The level of street-network sprawl in new development in Tuz Khormato followed a zig-zag trend.

How do development practices in Sala ad-Din fare in comparison to others in Iraq? Most recently in 2001-2014, street construction in Sala ad-Din was the 11th-most disconnected out of the 18 regions in Iraq. Its position in the ranks since 1975 has risen; relative to other regions in Iraq, street construction in Sala ad-Din has become more disconnected. Sala ad-Din ranked 17th in 1975, 9th in 1976-1990, 3rd in 1991-2000 and 11th in 2001-2014.

As of 2014, the city with the most disconnected street network in Sala ad-Din is Hamdi al Bajaji with an SNDi of 3.75, which is highly disconnected. Conversely, the most connected city is Tuz Khormato with an SNDi of 0.96, which is relatively well-connected. See trends for these cities: Tuz Khormato, Hamdi al Bajaji

The level of street-network sprawl in the aggregate network in Sala ad-Din rose steadily. To get a sense of how the aggregate street network has changed in Sala ad-Din, we can consider three of its most populous cities: At Tarimiyah, Hamdi al Bajaji and Tuz Khormato. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in the aggregate network in At Tarimiyah was at its lowest in 1976-1990. The level of street-network sprawl in the aggregate network in Hamdi al Bajaji peaked in 1991-2000. The level of street-network sprawl in the aggregate network in Tuz Khormato followed a zig-zag trend.

To date, Sala ad-Din is the 10th-most disconnected out of the 18 regions in Iraq. Its position in the ranks since 1975 has risen; relative to other regions in Iraq, the street network in Sala ad-Din has become more disconnected. Sala ad-Din ranked 17th in 1975, 10th in 1976-1990, 11th in 1991-2000 and 10th in 2001-2014.