Street-network Sprawl in Sri Lanka

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.

Sri Lanka

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 Sri Lanka on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Sri Lanka as of 2014, the overall level of street-network sprawl is 5.62, which is highly disconnected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 4.01, 6.0, 5.47 and 5.95. Disconnectivity in street construction in Sri Lanka follows a zig-zag trend. In 1975, street construction was most disconnected, while construction was most connected in 1976-1990.

Quantity of street network construction: The street network in Sri Lanka spans a total of 57459 kilometers. The period with the greatest volume of street construction was 1976-1990. These roads have an SNDi of 6.0, 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 4.01, 5.59, 5.58 and 5.62. Disconnectivity in Sri Lanka's street network follows a zig-zag trend. In 1975, the country was most disconnected; while it was most connected in 2001-2014.

The level of street-network sprawl in new development in Sri Lanka followed a zig-zag trend with an overall increase. To get a sense of how street development has changed in Sri Lanka, we can consider three of its most populous regions: Colombo, Kandy and Ampara. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in new development in Colombo peaked in 1991-2000. The level of street-network sprawl in new development in Kandy followed a zig-zag trend. The level of street-network sprawl in new development in Ampara was at its lowest in 1976-1990.

How do development practices in Sri Lanka fare in comparison to others in the world? Most recently in 2001-2014, street construction in Sri Lanka was the 34th-most disconnected out of the 155 countries in the world. Its position in the ranks since 1975 has risen; relative to other countries in the world, street construction in Sri Lanka has become more disconnected. Sri Lanka ranked 40th in 1975, 9th in 1976-1990, 38th in 1991-2000 and 34th in 2001-2014.

The largest city in Sri Lanka is Colombo, with a population of 4303600 people. Taking into account the entire (i.e. aggregate) street network in Colombo as of 2014, the overall level of street-network sprawl is 6.74, which is highly disconnected. The level of street-network sprawl in new development in Colombo rose steadily.

As of 2014, the city with the most disconnected street network in Sri Lanka is Badulla with an SNDi of 6.8, which is highly disconnected. Conversely, the most connected city is Sammanturai with an SNDi of 0.48, which is relatively well-connected. See trends for these cities: Sammanturai, Badulla

The level of street-network sprawl in the aggregate network in Sri Lanka followed a zig-zag trend with an overall increase. To get a sense of how the aggregate street network has changed in Sri Lanka, we can consider three of its most populous regions: Colombo, Kandy and Ampara. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in the aggregate network in Colombo rose steadily. The level of street-network sprawl in the aggregate network in Kandy followed a zig-zag trend. The level of street-network sprawl in the aggregate network in Ampara was at its lowest in 1976-1990.

To date, Sri Lanka is the 10th-most disconnected out of the 155 countries in the world. Its position in the ranks since 1975 has risen; relative to other countries in the world, the street network in Sri Lanka has become more disconnected. Sri Lanka ranked 40th in 1975, 8th in 1976-1990, 10th in 1991-2000 and 10th in 2001-2014.

The largest city in Sri Lanka is Colombo, with a population of 4303600 people. Taking into account the entire (i.e. aggregate) street network in Colombo as of 2014, the overall level of street-network sprawl is 6.74, which is highly disconnected. The level of street-network sprawl in the aggregate network in Colombo rose steadily.