Street-network Sprawl in Saint-Étienne, 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.

Saint-Étienne: city in Auvergne-Rhône-Alpes, 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 Saint-Étienne, France on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Saint-Étienne as of 2014, the overall level of street-network sprawl is 2.47, 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 1.79, 4.99, 6.66 and 7.26. In each period, new street development in Saint-Étienne steadily grows more disconnected than in the last. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 3.19 points, but between 1991-2000 and 2001-2014, it rose by just 0.6.

Quantity of street network construction: The street network in Saint-Étienne spans a total of 647 kilometers. It is dominated by roads constructed prior to 1975. These roads have an SNDi of 1.79, 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 1.79, 2.44, 2.45 and 2.47. Overall, the SNDi of the aggregate street network has risen: the street network in Saint-Étienne has become more disconnected. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 0.65 points, but between 1991-2000 and 2001-2014, it rose by just 0.03.

Saint-Étienne and Auvergne-Rhône-Alpes do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Saint-Étienne rose steadily, while the SNDi of street constructions in Auvergne-Rhône-Alpes peaked in 1991-2000.

How do development practices in Saint-Étienne fare in comparison to others in Auvergne-Rhône-Alpes? Most recently in 2001-2014, street construction in Saint-Étienne was the 2nd-most disconnected out of the 7 cities in Auvergne-Rhône-Alpes. Its position in the ranks since 1975 has risen; relative to other cities in Auvergne-Rhône-Alpes, street construction in Saint-Étienne has become more disconnected. Saint-Étienne ranked 5th in 1975, 1st in 1976-1990, 3rd in 1991-2000 and 2nd in 2001-2014.

Saint-Étienne and France follow the same trend in the disconnectivity of their street network constructions. The SNDi for both of these rose steadily.

How do development practices in Saint-Étienne fare in comparison to others in France? Most recently in 2001-2014, street construction in Saint-Étienne was the 7th-most disconnected out of the 76 cities in France. Its position in the ranks since 1975 has risen; relative to other cities in France, street construction in Saint-Étienne has become more disconnected. Saint-Étienne ranked 47th in 1975, 9th in 1976-1990, 6th in 1991-2000 and 7th in 2001-2014.

Saint-Étienne and Auvergne-Rhône-Alpes follow the same trend in the disconnectivity of their aggregate street networks. The SNDi for both of these rose steadily.

To date, Saint-Étienne is the 4th-most disconnected out of the 7 cities in Auvergne-Rhône-Alpes. Its position in the ranks since 1975 has risen; relative to other cities in Auvergne-Rhône-Alpes, the street network in Saint-Étienne has become more disconnected. Saint-Étienne ranked 5th in 1975, 4th in 1976-1990, 4th in 1991-2000 and 4th in 2001-2014.

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

To date, Saint-Étienne is the 33rd-most disconnected out of the 76 cities in France. Its position in the ranks since 1975 has risen; relative to other cities in France, the street network in Saint-Étienne has become more disconnected. Saint-Étienne ranked 47th in 1975, 33rd in 1976-1990, 33rd in 1991-2000 and 33rd in 2001-2014.

As of 2015, Saint-Étienne had a built-up area of 32.02 square kilometers, and a population of 172765 people.

These are some other cities with approximately the same population: