Street-network Sprawl in Bulgaria

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.

Bulgaria

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 Bulgaria on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Bulgaria as of 2014, the overall level of street-network sprawl is 2.22, which is relatively well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 1.83, 2.23, 4.72 and 4.43. Street construction in Bulgaria increased in disconnectivity initially but has since improved. The streets constructed in 1991-2000 were the most disconnected.

Quantity of street network construction: The street network in Bulgaria spans a total of 81642 kilometers. It is dominated by roads constructed in 1976-1990. These roads have an SNDi of 2.23, 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 1.83, 2.08, 2.16 and 2.22. Overall, the SNDi of the aggregate street network has risen: the street network in Bulgaria has become more disconnected. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 0.25 points, but between 1991-2000 and 2001-2014, it rose by just 0.06.

The level of street-network sprawl in new development in Bulgaria peaked in 1991-2000. To get a sense of how street development has changed in Bulgaria, we can consider three of its most populous regions: Grad Sofiya, Plovdiv and Varna. Out of the three regions, Plovdiv does not follow the same trend as the country. The level of street-network sprawl in new development in Plovdiv rose steadily.

How do development practices in Bulgaria fare in comparison to others in the world? Most recently in 2001-2014, street construction in Bulgaria was the 74th-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 Bulgaria has become more disconnected. Bulgaria ranked 124th in 1975, 120th in 1976-1990, 57th in 1991-2000 and 74th in 2001-2014.

The largest city in Bulgaria is Sofia, with a population of 926900 people. Taking into account the entire (i.e. aggregate) street network in Sofia as of 2014, the overall level of street-network sprawl is 0.96, which is relatively well-connected. The level of street-network sprawl in new development in Sofia peaked in 1991-2000.

As of 2014, the city with the most disconnected street network in Bulgaria is Buhovo with an SNDi of 2.67, which is in the 40th to 60th percentile of disconnectedness. Conversely, the most connected city is Burgas with an SNDi of 0.83, which is relatively well-connected. See trends for these cities: Burgas, Buhovo

The level of street-network sprawl in the aggregate network in Bulgaria rose steadily. To get a sense of how the aggregate street network has changed in Bulgaria, we can consider three of its most populous regions: Grad Sofiya, Plovdiv and Varna. Disconnectivity in the most populous cities in Bulgaria follow the same country trend.

To date, Bulgaria is the 129th-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, the street network in Bulgaria has become more connected. Bulgaria ranked 124th in 1975, 124th in 1976-1990, 124th in 1991-2000 and 129th in 2001-2014.

The largest city in Bulgaria is Sofia, with a population of 926900 people. Taking into account the entire (i.e. aggregate) street network in Sofia as of 2014, the overall level of street-network sprawl is 0.96, which is relatively well-connected. The level of street-network sprawl in the aggregate network in Sofia rose steadily.