CTwalk Map is an interactive web tool that seeks to highlight the
social cohesion potential of neighbourhoods while unmasking local access.
Utilizing population, location, and pedestrian network data from open
sources, it estimates the number of individuals from different age groups
who can reach city destinations within a 5 or 15-minute walk, highlighting
opportunities for social cohesion and access inequities.
Transparency is a key feature of CTwalk Map. It openly acknowledges
limitations in the available data, encouraging further data collection and
refinement. Users navigate the map through a user-friendly interface and
explore different destinations. They are encouraged to identify anomalies in
the map and scrutinize the completeness of the used data sources.
Furthermore, it serves an educational purpose by enhancing public
understanding of the relationship between AI, urban design, accessibility,
and social cohesion. It simplifies complex concepts and provides in-depth
insights into how street networks shape accessibility, empowering citizens
to actively participate in urban planning discussions.
Vasileios Milias
(Βασίλης Μηλιάς)
My research spans the fields of urban mobility and urban analytics. Within these domains, I focus on developing computational methods, tools, and indicators for evaluating the degree to which urban areas are (co)accessible, walkable, inclusive, sustainable, safe, and attractive for all. Through my work, I aim to support the UN's SDG 11: "Make cities and human settlements inclusive, safe, resilient and sustainable".
In 2024, I obtained my PhD in Urban Analytics at TU Delft , as a member of the Urban Analytics Lab. In my PhD, I introduced and studied the concept of urban co-accessibility: a destination’s potential to bring together different individuals and individuals from diverse demographic groups. Throughout this work, I engaged in an in-depth investigation of urban accessibility, spatial data science, and machine learning .
News
Published a policy paper "A practitioner-guided framework for urban analysis software" in collaboration with AMS institute. Read HERE
Discussed in SKAI Radio with Katerina Drakou about CThood and how to study to what degree Athens is a 15-minute city. Listen HERE (starting at 25').
Interviewed by ΝEWS247 about CThood and to what degree Athens is a 15-minute city. Read HERE.
Published two papers in the CUPUM2025 conference, in London, UK, on CTWalk and on Population-specific factors of pedestrian accessibility
Co-organized and presented in a workshop entitled "" Walking the X-min City: Methods and implementations to assess walkability and pedestrian accessibility at the Agile2025 conference in Dresden (Germany).
Participated in a panel discussion at the Aristotelis Climate Forum in Athens. Check it HERE.
Lead the workshop on “X-min cities, pedestrian accessibility, and digital tools“, during the Urbanism Next Europe Conference in Amsterdam (Netherlands)
Obtained my PhD! Read my open access PhD dissertation entitled "Urban Co-accessibility" HERE
Presented my work at the ΕΣΧΣΑ - 1st Scientific Conference on Spatial Planning and Development (Thessaloniki, Greece). Read it in the book of abstracts HERE
Started working remotely as a Senior Researcher at AMS institute.
🏆 Won the first prize demo award for CTwalk MAp at the NWO ICT.OPEN conference.
Gave an invited talk at TNO on "CTwalk and CTstreets: Exploring Walkability and Pedestrian (Co)Accessibility through Interactive Maps".
Lead the workshop on “What Factors Impact Access to Public Spaces and for Whom?“, realized in the City Hall of Helsinki (Finland) with Equal-Life's researchers and stakeholders.
CTwalk Map featured in Rafagas Links "#2103: cities, biodiversity, minefield". Read HERE.
Published and presented a paper in the AGILE2023 conference, in Delft, Netherlands. Read HERE.
Published and presented a paper in the CUPUM2023 conference, in Montreal, Canada. Read HERE.
Lead the workshop on “What Factors Impact Access to Public Spaces and for Whom?“, with the support of the American Planning Association. Read HERE.
Presented CTwalk Map and how to map walking accessibility of different population groups at the National Program for Sustainable Digital Information Management Demo Day. Read HERE
Gave an invited talk at TU Delft’s CityAI Lab on computational methods for assessing accessibility.
Short CV
Work Experience
> 2025 - Present: Senior Researcher (Transform Transport, IT)
> 2024 - 2025: Senior Researcher (AMS institute, NL)
> 2020 - 2024: PhD Researcher (Urban Analytics Lab, TU Delft, NL)
> 2019 - 2020: Spatial Data Specialist (HERE Technologies, NL)
> Sept.-Feb. 2018: R&D Intern (Philips Lighting, NL)
> April-June 2015: Project assistant (MIT, U.S.)
My top picks
Research
Accessibility is a widely employed concept across a variety of
disciplines to evaluate the
degree to which individuals can reach a desired destination.
Conventionally, accessibility
is determined by the attractiveness of a destination and the
associated travel cost
to reach it.
However, existing place-based accessibility measures do not
differentiate
between destinations accessible to individuals from a single demographic group and
those accessible to individuals from diverse demographic groups.
This hinders
our ability
to discern the encounter potential of different destinations.
In my PhD research, I address this gap by introducing co-accessibility as a measure of how accessible a given destination is to different individuals and demographic groups.
If you want to know more about urban co-accessibility you can read my dissertation HERE .
Too long? Then check below the short story of co-accessibility as a comic.
Relevant Projects
Here are some of the projects I have thoroughly enjoyed working on during the past years.
CThood
Interactive Map
Focus: X-minute City
(2025)
CThood, an open-access data-driven software tool designed to map the
access inequities withιn
the X-minute city paradigm. By leveraging open data sources, CThood
evaluates the accessibility
within 5- and 15-minute walking distances of 14 distinct types of places,
allowing users to identify
accessibility-related strengths and weaknesses of the X-minute
neighborhoods.
Combining an egalitarian and a sufficientarian perspective,
CThood assesses both how equally amenities are distributed and whether any
areas are excluded from basic,
essential services.
🏆 CTstreets Map
Interactive Map
Focus: Walkability
(2023)
CTstreets Map is an interactive web tool that seeks to highlight how
walkable are the streets of Amsterdam.
It uses granular population, location, and pedestrian network data from open
sources to estimate how walkable each street is.
It has been designed through a participatory approach involving urban
experts who live and work in Amsterdam.
It estimates the degree of walkability for the 5 and 15-minute walking areas
from each housing block in Amsterdam, revealing neighborhoods that encourage
walking and exposing disparities in walkability.
🏆
CTwalk Map
First prize demo award at the NWO ICT.OPEN
conference
Interactive Web Map
Mapping Pedestrian (co)Accessibility
(2023)
CTnetwork
Python Library
Focus: Accessibility &
Street Centrality Measures
(2023)
A Python library for calculating various street network centrality and
accessibility metrics, as well as the size and layout of surrounding
pedestrian and bicucly infrastructure.
(Co)accessibility
A Python library for calculating prospective social encounters between
persons from different demographic groups
Streetception
Python and Javascript toolkit
Capturing perceived qualities along
city streets
(2023)
A Python and Javascript toolkit for calculating perceived safety and
attractiveness of city streets through crowd parcipation.
Social Distancing Dashboard
The Social Distancing Dashboard offers interactive city maps that show
at street and neighborhood level whether people moving through public space
can keep to the distance rules. It provides an overview of various aspects –
such as the width of footpaths and the location of bus stops – that
influence the extent to which we can actually comply with the distance
rules. In this way, it can contribute to raising awareness of the
limitations that the design of public space entails and to decision-making
about COVID-19-related interventions in the city.
Equal Life
The EU-funded Equal-Life project will develop and utilise the exposome
concept in an integrated study of the external exposome and its social
aspects and of measurable internal physiological factors and link those to a
child's development and life course mental health. This will be done using a
novel approach combining exposure data to characterise, measure, model and
understand influences at different developmental stages. The goal is to
propose the best supportive environments for all children.
And here are some less relevant to my research but very fun projects I have also been a part of.
Dataslip
As we navigate the physical and digital world, we unknowingly leave
behind an immense trail of data. We are informed about this via short
statements (e.g., cookie popups) or lengthy documents (e.g., privacy
policies). However, even when we know that data is collected, we remain
largely unaware of its nature.
Dataslip is an interactive installation where the abstract notion of
personal data is translated into a material and tangible representation in
the form of a receipt. The receipt contains detailed information and
illustrative examples of the data generated from our interactions with five
different categories of products and services. Its length is proportional to
the amount of data collected about us.
Kaggle's Competition
The goal of this competition was to identify from which camera models,
images were taken. My team’s
solution was based on deep learning techniques using Python (Keras library).
Sentimental Airbnb
Collected data from Airbnb and Twitter and made a visualization that
shows color-coded clusters of areas with similar prices, the sentiment of
the tweets that have been sent in these areas and a wordcloud containing the
word-of-mouth as represented by these tweets.
Datasets
- 9700 ratings of outdoor spaces likely use for different activities (Likert scale 1-5)
- 6388 short explanations of these ratings
- Each location is linked to its corresponding google street view image
- To access the data set click HERE
- To access the related publication click HERE
> Street-based perceived safety and attractiveness scores for pedestrians (Frankfurt): ratings and reasoning.
- 7989 rating pairs of perceived safety and attractiveness
- 6388 short explanations of these ratings
- 403 participants and 753 locations
- 19114 and 18232keywords used to explain the safety and attractiveness ratings, respectively
- To access the data set click HERE
- To access the related publication click HERE
> Pedestrian Co-accessibility of urban places (Amsterdam, Rotterdam, The Hague, Utrecht, Eindhoven)
- Co-accessibility scores of different types of urban places considering 5,10,and 15-minute walksheds
- Total number of people who have access to each urban place
- Number of people per age group who have access to each urban place
- To access the data set click HERE
- To access related publications click HERE and for more details on the concept of co-accessibility click HERE
Conferences, Talks, Exhibitions & Workshops
> [2025] Agile2025 Conference - Co-organized and presented in a workshop entitled "" Walking the X-min City: Methods and implementations to assess walkability and pedestrian accessibility at the Agile2025 conference in Dresden (Germany).
> [2025] Aristotelis Climate Forum - Participated in a panel discussion at the Aristotelis Climate Forum in Athens (Greece).
> [2024] Urbanism Next Europe Conference - Lead the workshop on “X-min cities, pedestrian accessibility, and digital tools“, in Amsterdam (Netherlands).
> [2024] ΕΣΧΣΑ - Presented my work at the 1st Scientific Conference on Spatial Planning and Development (Thessaloniki, Greece), on "CTwalk and CTstreets: Mapping Walkability and Pedestrian (Co)Accessibility through open data".
> [2024] 🏆 NWO ICT.OPEN conference - Received the first prize demo award for CTwalk Map at the NWO ICT.OPEN conference.
> [2024] TNO - Invited talk on "CTwalk and CTstreets: Exploring Walkability and Pedestrian (Co)Accessibility through Interactive Maps"
> [2023] Dutch Design Week - Exhibiting CTwalk Map in the DDW2023 with the support of 4TU.Design United
> [2023] National Program for Sustainable Digital Information Management Demo Day - Demonstration of CTwalk Map and talk on "Mapping accessibility with urban analytics: measuring is knowing?"
> [2023] Equal Life (H2020) - Workshop on "What Factors Impact Access to Public Spaces and for Whom?" at the Equal-Life Stakeholder Forum, Helsinki, Finland
> [2023] CPM - Workshop with the support of the American Planning Association and the Consulting Planners of Massachusetts on "What Factors Impact Access to Public Spaces and for Whom?"
> [2023] NWO ΙCT.Open conference - Poster presentation at NWO ICT.Open conference in Utrecht, the Netherlands on "Crowdsourcing perceived qualities of city streets using street-level images."
> [2023] EHEN conference - Presentation at EHEN conference in Leuven, Belgium on "Exposure to street environment features and perceptions of safety and attractiveness."
> [2023] TU Defft's CityAI Lab - Invited talk on "Computational methods for assessing accessibility"
> [2023] Towards Healthy Society conference - Presentation during interactive market on "How can accessibility promote wellbeing?"
> [2022] HERE Technologies - Invited talk on "From POIs to Accessibility and Beyond"
> [2022] EHEN conference - Presentation at EHEN conference in Barcelona, Spain on "Co-accessibility: A new lens towards age-inclusive and accessible public spaces."
Relevant Publications
PhD Dissertation
Peer-reviewed
> Psyllidis, A., Milias, V., (2025). Population-specific factors of pedestrian accessibility: Bridging practitioner insights and accessibility metrics. 19th International Conference on Computers in Urban Planning and Urban Management.
> Milias, V., Psyllidis, A., Bozzon, A.(2024). Bridging or separating? Co-accessibility as a measure of potential place-based encounters Journal of Transport Geography, 121, 10427.
> Milias, V., Teeuwen, R., Bozzon, A., Psyllidis, A. (2024). Crowdsourcing the influence of physical features on the likely use of public open spaces? Computational Urban Science Journal, 4, 15.
> Milias, V., Sharifi Noorian, S., Bozzon, A., & Psyllidis, A. (2023). Is it safe to be attractive? Disentangling the influence of streetscape features on the perceived safety and attractiveness of city streets. AGILE: GIScience Series, 4, 8.
> Van Asten, T.*, Milias, V.*, Bozzon, A., & Psyllidis, A. (2023). “Eyes on the Street”: Estimating Natural Surveillance Along Amsterdam’s City Streets Using Street-Level Imagery. In International Conference on Computers in Urban Planning and Urban Management (pp. 215-229). Cham: Springer Nature Switzerland.
> Milias, V. & Psyllidis, A. (2022). Measuring spatial age segregation through the lens of co-accessibility to urban activities. Computers, Environment and Urban Systems, 95, 101829.
> Milias, V. & Psyllidis, A. (2021). Assessing the influence of point-of-interest features on the classification of place categories. Computers, Environment and Urban Systems, 86, 101597.
For a full list of my publications check my Google Scholar page
Media
> SKAI Radio (2025). Discussed with Katerina Drakou about CThood and how to study to
what degree Athens is a 15-minute city.
Listen here:
or check the entire episode HERE (starting at 25').
> Het Parool - Dutch Newspaper (2025). In a city like Boston, everyone runs faster and faster. Is Amsterdam still a city for strolling?. Featured in Het Parool discussing about people's walking behaviour in cities. I share insights on how urban design influences pedestrian behavior and why creating space for lingering is essential for vibrant, livable cities. (In Dutch)
> CHI NL - ICT.OPEN (2024). Featured in an article by CHI NL about receiving the ICT.OPEN Demo Award at the NWO ICT.OPEN conference.
> (TUD) Industrial Design Engineering News. (2023). New tool shows accessibility of public areas for different population groups. Article published by TU Delft about the CTwalk tool and my PhD research on co-accessibility.
> WHO - Book of abstracts. Towards the design of healthy and sustainable cities: What Factors Impact Access to Public Spaces and for Whom? Abstract for WHO European Healthy Cities Network Annual Business Meeting and Technical Conference.
>Onze Jeugd (Our Youth) (2023). Kinderen in de openbare ruimte. Urban Analytics Lab biedt inzicht in knelpunten leefomgeving (Children in public space) (The Urban Analytics Lab provides insight into bottlenecks in the living environment). .
> Open Access Government (2022). Equal-Life team: Improving child exposome and quality of life. Open Access Government.
Teaching
Courses
> Machine Learning for Design - Lectures/Tutorials, Assignments (BSc, IDE - TU Delft)
> Urban Data Science, Lectures/Tutorials, Assignments (BSc, IDE - TU Delft)
> AI for Society - Guest Lecture (MSc, IDE - TU Delft)
> MOOC for H2020 project "Periscope"
> Contributed to Advanced Machine Learning for Design (MSc, IDE - TU Delft)
> Moderator in Software Based Products (BSc, IDE - TU Delft)
Supervised MSc Students
> [2023] Charalampos Spanos (TU Delft Faculty of Architecture & the Built Environment). CONNECTING PLACES - CONNECTING PEOPLE: A network of public spaces as a backbone for social cohesion in South Rotterdam.