Street-network Sprawl in Nantes, France

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.

Nantes: city in Pays de la Loire, France

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 Nantes, France on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Nantes as of 2014, the overall level of street-network sprawl is 2.49, 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 2.31, 3.6, 2.51 and 2.94. Disconnectivity in street construction in Nantes 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 Nantes spans a total of 1803 kilometers. It is dominated by roads constructed prior to 1975. These roads have an SNDi of 2.31, which is in the 40th to 60th percentile of disconnectedness.

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 2.31, 2.49, 2.49 and 2.49. Disconnectivity in Nantes's street network follows a zig-zag trend. In 1975, the city was most disconnected; while it was most connected in 2001-2014.

Nantes and Pays de la Loire do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Nantes followed a zig-zag trend with an overall increase, while the SNDi of street constructions in Pays de la Loire peaked in 1991-2000.

How do development practices in Nantes fare in comparison to others in Pays de la Loire? Most recently in 2001-2014, street construction in Nantes was the 1st-most disconnected out of the 3 cities in Pays de la Loire. Its position in the ranks since 1975 has not changed. Nantes ranked 1st in 1975, 1st in 1976-1990, 2nd in 1991-2000 and 1st in 2001-2014.

Nantes and France do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Nantes followed a zig-zag trend with an overall increase, while the SNDi of street constructions in France rose steadily.

How do development practices in Nantes fare in comparison to others in France? Most recently in 2001-2014, street construction in Nantes was the 54th-most disconnected out of the 76 cities in France. Its position in the ranks since 1975 has fallen; relative to other cities in France, street construction in Nantes has become more connected. Nantes ranked 29th in 1975, 30th in 1976-1990, 49th in 1991-2000 and 54th in 2001-2014.

Nantes and Pays de la Loire do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Nantes followed a zig-zag trend with an overall increase, while the SNDi of street constructions in Pays de la Loire rose steadily.

To date, Nantes is the 1st-most disconnected out of the 3 cities in Pays de la Loire. Its position in the ranks since 1975 has not changed. Nantes ranked 1st in 1975, 1st in 1976-1990, 1st in 1991-2000 and 1st in 2001-2014.

Nantes and France do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Nantes followed a zig-zag trend with an overall increase, while the SNDi of street constructions in France rose steadily.

To date, Nantes is the 30th-most disconnected out of the 76 cities in France. Its position in the ranks since 1975 has fallen; relative to other cities in France, the street network in Nantes has become more connected. Nantes ranked 29th in 1975, 30th in 1976-1990, 30th in 1991-2000 and 30th in 2001-2014.

As of 2015, Nantes had a built-up area of 91.93 square kilometers, and a population of 436853 people.

These are some other cities with approximately the same population: