Street-network Sprawl in Purnia, India

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.

Purnia: city in Bihar, India

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 Purnia, India on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Purnia as of 2014, the overall level of street-network sprawl is 1.44, which is relatively well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 0.58, 1.01, 1.43 and 1.89. In each period, new street development in Purnia steadily grows more disconnected than in the last.

Quantity of street network construction: The street network in Purnia spans a total of 132 kilometers. It is dominated by roads constructed in 2001-2014. These roads have an SNDi of 1.89, 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 0.58, 1.0, 1.16 and 1.44. Overall, the SNDi of the aggregate street network has risen: the street network in Purnia has become more disconnected. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 0.42 points, but between 1991-2000 and 2001-2014, it rose by just 0.28.

Purnia and Bihar do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Purnia rose steadily, while the SNDi of street constructions in Bihar followed a zig-zag trend with an overall increase.

How do development practices in Purnia fare in comparison to others in Bihar? Most recently in 2001-2014, street construction in Purnia was the 44th-most disconnected out of the 120 cities in Bihar. Its position in the ranks since 1975 has fallen; relative to other cities in Bihar, street construction in Purnia has become more connected. Purnia ranked 31st in 1975, 63rd in 1976-1990, 29th in 1991-2000 and 44th in 2001-2014.

Purnia and India follow the same trend in the disconnectivity of their street network constructions. The SNDi for both of these rose steadily.

How do development practices in Purnia fare in comparison to others in India? Most recently in 2001-2014, street construction in Purnia was the 904th-most disconnected out of the 1716 cities in India. Its position in the ranks since 1975 has fallen; relative to other cities in India, street construction in Purnia has become more connected. Purnia ranked 714th in 1975, 956th in 1976-1990, 804th in 1991-2000 and 904th in 2001-2014.

Purnia and Bihar follow the same trend in the disconnectivity of their aggregate street networks. The SNDi for both of these rose steadily.

To date, Purnia is the 74th-most disconnected out of the 120 cities in Bihar. Its position in the ranks since 1975 has fallen; relative to other cities in Bihar, the street network in Purnia has become more connected. Purnia ranked 31st in 1975, 66th in 1976-1990, 69th in 1991-2000 and 74th in 2001-2014.

Purnia and India follow the same trend in the disconnectivity of their aggregate street networks. The SNDi for both of these rose steadily.

To date, Purnia is the 1187th-most disconnected out of the 1716 cities in India. Its position in the ranks since 1975 has fallen; relative to other cities in India, the street network in Purnia has become more connected. Purnia ranked 714th in 1975, 1063rd in 1976-1990, 1136th in 1991-2000 and 1187th in 2001-2014.

As of 2015, Purnia had a built-up area of 3.97 square kilometers, and a population of 347177 people.

These are some other cities with approximately the same population: