Find out more about co-accessibility in our open access journal paper HERE

What opportunities for social cohesion do cities provide?

Is your neighborhood park frequented by a homogenous or diverse mix of people? How many amenities can you reach within a short walking distance? And do you often encounter people from different walks of life?
This is what the interactive CTwalk Map seeks to highlight.

  • It uses granular population, location, and pedestrian network data from open sources to estimate how many children, adults, and elderly citizens can reach various destinations in a city within a short walk.

  • It offers a simple and in-depth understanding of how the 5 and 15 minute walking environments are shaped by the street network.

  • It estimates the degree of pedestrian co-accessibility of various city destinations to highlight the social cohesion potential of neighborhoods while also unmasking local access inequities.


[Νοv. 2023]
The family of CTwalk is growing. CTstreets is now available online!
[Oct. 2023]
Exhibited at the Dutch Design Week 2023. Read HERE.
[Sept. 2023] Featured in a short news article in Delft Design Stories. Read HERE.
[Aug. 2023] Featured in #73: La Cultura Del Dato newsletter by Stefano Gatti. Read HERE.
[July 2023] Featured in Rafagas Links "#2103: cities, biodiversity, minefield". Read HERE.
[June 2023] Featured in #521: quantum of sollazzo newsletter by puntofisso. Read HERE.
[June 2023] Featured in the beSpacific blog. Read HERE.
[May 2023] Presented at the National Program for Sustainable Digital Information Management Demo Day. Read HERE

Open Data

Left image

Population Demographics

CTwalk Map uses the Dutch Central Bureau of Statistics (Centraal Bureau voor de Statistiek, 2020) to collect granular data on population demographics (including household location and age) at a 100 × 100 m2 grid level.

Our population demographics concern the year 2020. We group residents into three population age categories: children (0–15 years old), adolescents and adults (16–64 years old), and the elderly (equal or above 65 years of age).

Right image

Pedestrian Network

CTwalk Map uses OpenStreetMap (OSM) , an open-source mapping platform containing worldwide geographical data, to collect data on the pedestrian network.

More specifically, the OSMnx package was used to extract walkable streets, by setting the network type to “walk”. In this way, streets categories unrelated to pedestrian movement such as motorways, service roads and cycleways are excluded.

OSM data were collected in November 2021.


The selection of the places to be included is influenced by Ray Oldenburg's definition of the “third places” (i.e., “public places that host the regular, voluntary, informal, and happily anticipated gatherings of individuals beyond the realms of home and work”). In other words, places where people of different ages can perform activities and socially interact with each other.



Pedestrian Accessibility

We use different walksheds to determine which places are within walking distance of each origin (i.e., homes). We employ buffers that correspond to 5- and 15-minute walking distances. We use the average walking speed of 1.26 m/s (i.e., the average of all age groups) to delineate these walksheds. Specifically:

[STEP 1] We represent the walkable street network as a graph. The edges of the graph represent streets, while the nodes represent the street intersections.

[STEP 2] We find the network node that is closest to the centroid (i.e., the geometrical center) of each grid cell. The generated node indicates a person’s estimated home location and serves as the starting point for further analysis.

[STEP 3] We measure pedestrian accessibility to various destinations by calculating walking trips from the origins, weighted by the length of each street segment, and taking into account the above-mentioned average walking speed.

[STEP 4] In this way, we compute the areas that can be reached on foot in 5 and 15-minute journeys and locate the places that are inside these areas.

Co-accessibility & age diversity metric

To calculate the degree of co-accessibility and the corresponding age diversity metric for each destination:

[STEP 1] We calculate the total number of people who have access to each destination within the 5 and 15-minute walksheds.

[STEP 2] We calculate how many of these people are in each age group.

[STEP 3] We use Shannon’s Equitability Index (EI) to determine the age diversity of everyone who has access to each destination:

EI = - ln P i × P i ln k

[STEP 4] We label each place as Low (values lower than average), Average (values around average) , or High (values higher than average), depending on the age diversity (or the number of children or elderly citizens) of the people who can access to each destination.


The Layers

There are 3 primary layers that can be toggled on and off in the upper left of the map.

The walkable street network: The walkable street network we used to calculate the walksheds from OpenStreetMap.

Population Demographics: People's residences at a spatial resolution of 100x100m2 (CBS data).

Places collected : Turn it on to view the places we collected from OpenStreetMap.

The walksheds

Hovering over the CTwalk Map will display the 5 and 15-minute walksheds.

To switch between the 5 and 15-minute walksheds, click the “5 minutes” or “15 minutes” buttons in the upper left of the map, respectively.

Accessibility & Equity

By clicking on the population blocks are colored based on the number of places people can reach within a 5 or 15-minute walk.

This layer will become invisible if you click the again.

How many places are accessible from each location?

When you zoom in on the map and click on any walkshed, a popup will open displaying the number and type of places that people of that area can access within a 5 or 15-minute walk, as well as the size of the related walking area.

Co-accessibility & age diversity

How many people of each age group can access a place within a 5 or 15-minute walk?

If you click on any location, a window will open with information about that place, how many individuals can access it within a 5 or 15-minute walk from their home, and how diverse these people are in terms of age.

The color of each location indicates whether the age diversity (or number of children or elderly citizens) is lower, almost equal, or higher than the national average.

On the upper left of the map, you may decide which value will be used to color-code the places by clicking on the "Age Diversity", "Children", or "Elderly" buttons.

Map Style

By clicking on the , , or buttons in the upper right corner of the map will re-initialize and modify the style of the entire map.


By selecting the "Other Cities" button, at the top right of the map, you may view the same map for additional cities.

So far, the cities that are available are the five largest cities in the Netherlands: Amsterdam, Rotterdam, The Hague, Utrecht, and Eindhoven.


CTwalk Map is an interactive web tool developed as part of research conducted by Vasileios Milias during his doctoral studies at the Urban Analytics Lab within the Knowledge and Intelligence Design group at Delft University of Technology.

The Urban Analytics Lab developed a set of human-centered metrics, indicators, and software tools to measure and evaluate urban design qualities that lead to more walkable, sustainable, healthy, and welcoming cities for all. The CTwalk Map is a prime example of one of these tools.

If you like this project check also CTstreets Map: mapping walkability in Amsterdam

CTwalk's Team

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Vasileios Milias
PhD Candidate | Urban Analytics Lab

> Personal Website: VMilias
> Linkedin: vmilias
> Github: MiliasV

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Achilleas Psyllidis
Assistant Professor | Director of Urban Analytics Lab

>Email: a.psyllidis[at]

> Linkedin: achilleaspsyllidis
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Alessandro Bozzon
Professor of Human-Centered Artificial Intelligence

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Knowledge and Intelligence
Design Group (KiND)

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Delf University of Technology