Street-network Sprawl in Busan, South Korea

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.

Busan: city in South Korea

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 Busan, South Korea on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Busan as of 2014, the overall level of street-network sprawl is 1.42, which is relatively well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 1.15, 2.37, 2.19 and 2.17. Street construction in Busan increased in disconnectivity initially but has since improved. The streets constructed in 1976-1990 were the most disconnected.

Quantity of street network construction: The street network in Busan spans a total of 3975 kilometers. It is dominated by roads constructed prior to 1975. These roads have an SNDi of 1.15, 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 1.15, 1.38, 1.41 and 1.42. Overall, the SNDi of the aggregate street network has risen: the street network in Busan has become more disconnected. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 0.23 points, but between 1991-2000 and 2001-2014, it rose by just 0.0.

Busan and Busan do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Busan peaked in 1976-1990, while the SNDi of street constructions in Busan followed a zig-zag trend with an overall increase.

How do development practices in Busan fare in comparison to others in Busan? Most recently in 2001-2014, street construction in Busan was the 1st-most disconnected out of the 1 cities in Busan. Its position in the ranks since 1975 has not changed. Busan ranked 1st in 1975, 1st in 1976-1990, 1st in 1991-2000 and 1st in 2001-2014.

Busan and South Korea do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Busan peaked in 1976-1990, while the SNDi of street constructions in South Korea rose steadily.

How do development practices in Busan fare in comparison to others in South Korea? Most recently in 2001-2014, street construction in Busan was the 19th-most disconnected out of the 39 cities in South Korea. Its position in the ranks since 1975 has fallen; relative to other cities in South Korea, street construction in Busan has become more connected. Busan ranked 9th in 1975, 4th in 1976-1990, 12th in 1991-2000 and 19th in 2001-2014.

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

To date, Busan is the 1st-most disconnected out of the 1 cities in Busan. Its position in the ranks since 1975 has not changed. Busan ranked 1st in 1975, 1st in 1976-1990, 1st in 1991-2000 and 1st in 2001-2014.

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

To date, Busan is the 11th-most disconnected out of the 39 cities in South Korea. Its position in the ranks since 1975 has fallen; relative to other cities in South Korea, the street network in Busan has become more connected. Busan ranked 9th in 1975, 10th in 1976-1990, 10th in 1991-2000 and 11th in 2001-2014.

As of 2015, Busan had a built-up area of 183.0 square kilometers, and a population of 3431209 people.

These are some other cities with approximately the same population:

For some related information about population, urban extent and density, and roads, visit the Atlas of Urban Expansion.