Street-network Sprawl in Parwan, Afghanistan

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.

Parwan: region in Afghanistan

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 Parwan, Afghanistan on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Parwan as of 2014, the overall level of street-network sprawl is 4.42, which is highly disconnected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 7.97, 3.47, 4.15 and 1.95. Disconnectivity in street construction in Parwan follows a zig-zag trend. In 2001-2014, street construction was most disconnected, while construction was most connected in 1975.

Quantity of street network construction: The street network in Parwan spans a total of 605 kilometers. It is dominated by roads constructed prior to 1975. These roads have an SNDi of 7.97, 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 7.97, 5.04, 4.9 and 4.42. Overall, the SNDi of the aggregate street network has fallen: the street network in Parwan has become more connected.

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

How do development practices in Parwan fare in comparison to others in Afghanistan? Most recently in 2001-2014, street construction in Parwan was the 21st-most disconnected out of the 25 regions in Afghanistan. Its position in the ranks since 1975 has fallen; relative to other regions in Afghanistan, street construction in Parwan has become more connected. Parwan ranked 4th in 1975, 12th in 1976-1990, 15th in 1991-2000 and 21st in 2001-2014.

As of 2014, the city with the most disconnected street network in Parwan is Bagram with an SNDi of 4.17, which is highly disconnected. Conversely, the most connected city is Charikar with an SNDi of 1.46, which is relatively well-connected. See trends for these cities: Charikar, Bagram

The level of street-network sprawl in the aggregate network in Parwan fell steadily. To get a sense of how the aggregate street network has changed in Parwan, we can consider two of its most populous cities: Charikar and Bagram. Out of the two cities, Bagram does not follow the same trend as the region. The level of street-network sprawl in the aggregate network in Bagram followed a zig-zag trend.

To date, Parwan is the 16th-most disconnected out of the 25 regions in Afghanistan. Its position in the ranks since 1975 has fallen; relative to other regions in Afghanistan, the street network in Parwan has become more connected. Parwan ranked 4th in 1975, 15th in 1976-1990, 16th in 1991-2000 and 16th in 2001-2014.