Street-network Sprawl in NCT of Delhi, India

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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:

• nodal degree
• dendricity, the tree-likeness of the street network
• circuity, the ratio of the distance by road to the straight-line distance of two locations on the street network
• sinuosity, the curviness of a street

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:

• Global trends toward urban street-network sprawl
• A global assessment of street-network sprawl

To see the state of street-network sprawl across the globe, visit the sprawlmap.

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NCT of Delhi: region in 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 NCT of Delhi, India on the sprawlmap

How have NCT of Delhi's street networks changed over time?

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in NCT of Delhi as of 2014, the overall level of street-network sprawl is 3.58, which is highly disconnected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 3.38, 3.56, 3.88 and 5.43. In each period, new street development in NCT of Delhi steadily grows more disconnected than in the last.

Quantity of street network construction: The street network in NCT of Delhi spans a total of 13896 kilometers. It is dominated by roads constructed in 1976-1990. These roads have an SNDi of 3.56, 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 3.38, 3.48, 3.52 and 3.58. Overall, the SNDi of the aggregate street network has risen: the street network in NCT of Delhi has become more disconnected. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 0.1 points, but between 1991-2000 and 2001-2014, it rose by just 0.06.

NCT of Delhi in context: Street-network sprawl of new development

The level of street-network sprawl in new development in NCT of Delhi rose steadily. To get a sense of how street development has changed in NCT of Delhi, we can consider two of its most populous cities: Delhi [New Delhi] and Salhapur. Disconnectivity in the most populous cities in NCT of Delhi follow the same region trend.

How do development practices in NCT of Delhi fare in comparison to others in India? Most recently in 2001-2014, street construction in NCT of Delhi was the 14th-most disconnected out of the 35 regions in India. Its position in the ranks since 1975 has risen; relative to other regions in India, street construction in NCT of Delhi has become more disconnected. NCT of Delhi ranked 24th in 1975, 22nd in 1976-1990, 27th in 1991-2000 and 14th in 2001-2014.

NCT of Delhi in context: Aggregate street-network sprawl

As of 2014, the city with the most disconnected street network in NCT of Delhi is Salhapur with an SNDi of 4.44, which is highly disconnected. Conversely, the most connected city is Delhi [New Delhi] with an SNDi of 3.49, which is highly disconnected. See trends for these cities: Delhi [New Delhi], Salhapur

The level of street-network sprawl in the aggregate network in NCT of Delhi rose steadily. To get a sense of how the aggregate street network has changed in NCT of Delhi, we can consider two of its most populous cities: Delhi [New Delhi] and Salhapur. Disconnectivity in the most populous cities in NCT of Delhi follow the same region trend.

To date, NCT of Delhi is the 26th-most disconnected out of the 35 regions in India. Its position in the ranks since 1975 has fallen; relative to other regions in India, the street network in NCT of Delhi has become more connected. NCT of Delhi ranked 24th in 1975, 22nd in 1976-1990, 23rd in 1991-2000 and 26th in 2001-2014.

Cities in NCT of Delhi

• Delhi [New Delhi]
• Salhapur