Street-network Sprawl in Caen, France

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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:

• nodal degree
• dendricity, the tree-likeness of the street network
• circuity, the ratio of the distance by road to the straight-line distance of two locations on the street network
• sinuosity, the curviness of a street

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:

• Global trends toward urban street-network sprawl
• A global assessment of street-network sprawl

To see the state of street-network sprawl across the globe, visit the sprawlmap.

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Caen: city in Normandie, 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 Caen, France on the sprawlmap

How have Caen's street networks changed over time?

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Caen as of 2014, the overall level of street-network sprawl is 1.96, which is relatively well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 1.8, 2.58, 2.85 and 3.07. In each period, new street development in Caen steadily grows more disconnected than in the last. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 0.79 points, but between 1991-2000 and 2001-2014, it rose by just 0.22.

Quantity of street network construction: The street network in Caen spans a total of 828 kilometers. It is dominated by roads constructed prior to 1975. These roads have an SNDi of 1.8, 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 1.8, 1.89, 1.93 and 1.96. Overall, the SNDi of the aggregate street network has risen: the street network in Caen has become more disconnected. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 0.09 points, but between 1991-2000 and 2001-2014, it rose by just 0.03.

Caen in context: Street-network sprawl of new development

Caen and Normandie 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 Caen fare in comparison to others in Normandie? Most recently in 2001-2014, street construction in Caen was the 3rd-most disconnected out of the 4 cities in Normandie. Its position in the ranks since 1975 has not changed. Caen ranked 3rd in 1975, 4th in 1976-1990, 3rd in 1991-2000 and 3rd in 2001-2014.

Caen 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 Caen fare in comparison to others in France? Most recently in 2001-2014, street construction in Caen was the 50th-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 Caen has become more connected. Caen ranked 46th in 1975, 59th in 1976-1990, 42nd in 1991-2000 and 50th in 2001-2014.

Caen in context: Aggregate street-network sprawl

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

To date, Caen is the 3rd-most disconnected out of the 4 cities in Normandie. Its position in the ranks since 1975 has not changed. Caen ranked 3rd in 1975, 3rd in 1976-1990, 3rd in 1991-2000 and 3rd in 2001-2014.

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

To date, Caen is the 53rd-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 Caen has become more connected. Caen ranked 46th in 1975, 55th in 1976-1990, 52nd in 1991-2000 and 53rd in 2001-2014.

What about other similarly-populated cities?

As of 2015, Caen had a built-up area of 48.26 square kilometers, and a population of 164787 people.

These are some other cities with approximately the same population:

• Nazareth, Israel
• Kherli, India
• Rushan, China