Street-network Sprawl in Ann Arbor, United States

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.

Ann Arbor: city in Michigan, United States

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 Ann Arbor, United States on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Ann Arbor as of 2014, the overall level of street-network sprawl is 2.18, which is relatively well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 1.66, 2.67, 4.88 and 4.73. Street construction in Ann Arbor 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 Ann Arbor spans a total of 466 kilometers. It is dominated by roads constructed prior to 1975. These roads have an SNDi of 1.66, 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 1.66, 2.04, 2.17 and 2.18. Overall, the SNDi of the aggregate street network has risen: the street network in Ann Arbor has become more disconnected. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 0.37 points, but between 1991-2000 and 2001-2014, it rose by just 0.01.

Ann Arbor and Michigan do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Ann Arbor peaked in 1991-2000, while the SNDi of street constructions in Michigan rose steadily.

How do development practices in Ann Arbor fare in comparison to others in Michigan? Most recently in 2001-2014, street construction in Ann Arbor was the 7th-most disconnected out of the 9 cities in Michigan. Its position in the ranks since 1975 has fallen; relative to other cities in Michigan, street construction in Ann Arbor has become more connected. Ann Arbor ranked 6th in 1975, 9th in 1976-1990, 8th in 1991-2000 and 7th in 2001-2014.

Ann Arbor and United States follow the same trend in the disconnectivity of their street network constructions. The SNDi for both of these peaked in 1991-2000.

How do development practices in Ann Arbor fare in comparison to others in United States? Most recently in 2001-2014, street construction in Ann Arbor was the 191st-most disconnected out of the 315 cities in United States. Its position in the ranks since 1975 has risen; relative to other cities in United States, street construction in Ann Arbor has become more disconnected. Ann Arbor ranked 251st in 1975, 278th in 1976-1990, 203rd in 1991-2000 and 191st in 2001-2014.

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

To date, Ann Arbor is the 7th-most disconnected out of the 9 cities in Michigan. Its position in the ranks since 1975 has fallen; relative to other cities in Michigan, the street network in Ann Arbor has become more connected. Ann Arbor ranked 6th in 1975, 7th in 1976-1990, 6th in 1991-2000 and 7th in 2001-2014.

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

To date, Ann Arbor is the 254th-most disconnected out of the 315 cities in United States. Its position in the ranks since 1975 has fallen; relative to other cities in United States, the street network in Ann Arbor has become more connected. Ann Arbor ranked 251st in 1975, 251st in 1976-1990, 247th in 1991-2000 and 254th in 2001-2014.

As of 2015, Ann Arbor had a built-up area of 28.05 square kilometers, and a population of 81129 people.

These are some other cities with approximately the same population: