Street-network Sprawl in Iceland

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.

Iceland

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 Iceland on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Iceland as of 2014, the overall level of street-network sprawl is 2.64, which is in the 40th to 60th percentile of disconnectedness.

Trends in street network construction: The SNDis of street construction for the respective time periods are 2.01, nan, 3.77 and 3.39. Data was not available in 1976-1990.

Quantity of street network construction: The street network in Iceland spans a total of 2945 kilometers. It is dominated by roads constructed in 2001-2014. These roads have an SNDi of 3.39, 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 2.01, 2.01, 2.3 and 2.64. Overall, the SNDi of the aggregate street network has risen: the street network in Iceland has become more disconnected.

The level of street-network sprawl in new development in Iceland followed a zig-zag trend with an overall increase. To get a sense of how street development has changed in Iceland, we can consider one of its most populous regions: Höfuðborgarsvæði. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in new development in Höfuðborgarsvæði followed a zig-zag trend with an overall increase.

How do development practices in Iceland fare in comparison to others in the world? Most recently in 2001-2014, street construction in Iceland was the 117th-most disconnected out of the 155 countries in the world. Its position in the ranks since 1975 has fallen; relative to other countries in the world, street construction in Iceland has become more connected. Iceland ranked 115th in 1975, 93rd in 1991-2000 and 117th in 2001-2014. There was no ranking in 1976-1990 due to unavailable data.

The largest city in Iceland is Reykjavik, with a population of 184400 people. Taking into account the entire (i.e. aggregate) street network in Reykjavik as of 2014, the overall level of street-network sprawl is 1.73, which is relatively well-connected. The level of street-network sprawl in new development in Reykjavik followed a zig-zag trend with an overall increase.

As of 2014, the city with the most disconnected street network in Iceland is Reykjavik with an SNDi of 1.73, which is relatively well-connected. Conversely, the most connected city is Reykjavik with an SNDi of 1.73, which is relatively well-connected. See trends for these cities: Reykjavik, Reykjavik

The level of street-network sprawl in the aggregate network in Iceland rose steadily. To get a sense of how the aggregate street network has changed in Iceland, we can consider one of its most populous regions: Höfuðborgarsvæði. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in the aggregate network in Höfuðborgarsvæði rose steadily.

To date, Iceland is the 112th-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 Iceland has become more disconnected. Iceland ranked 115th in 1975, 129th in 1976-1990, 119th in 1991-2000 and 112th in 2001-2014.

The largest city in Iceland is Reykjavik, with a population of 184400 people. Taking into account the entire (i.e. aggregate) street network in Reykjavik as of 2014, the overall level of street-network sprawl is 1.73, which is relatively well-connected. The level of street-network sprawl in the aggregate network in Reykjavik rose steadily.