An interactive visualisation of the Car Dependency Index (CDI), a high-resolution measure that compares opportunity access by private car versus public transport for every ~200 m hexagonal cell of a city.
CDI is defined as
CDI = (O_car − O_PT) / (O_car + O_PT)
so it ranges from −1 (PT-favoured) through 0 (balanced) to +1 (car-dependent).
The viewer accompanies the paper Car Dependency in Urban Accessibility by Campanelli, Marzolla, Bruno, Melo & Loreto (2026 · arXiv:2604.01019) by the Sustainable Cities team at Sony CSL - Rome. See all platforms here: https://linktr.ee/sonycsl_cities_platforms.
- World landing map — pins for every city in
data/index.json. Cities with bundled hex-level data are highlighted in red; others are dimmed and carry a no data badge. - City view — three-panel layout:
- Cartogram with a continuous blue ↔ white ↔ red CDI gradient.
- Sidebar with: scale legend, dual-thumb CDI range filter, live city summary, selected-hexagon inspector and interaction tips.
- Scatter plot of opportunity-by-car (x) vs. opportunity-by-PT (y), with the y = x diagonal marking CDI = 0. Cross-highlights with the map.
- Compare cities (Stats view) — diverging bar chart of population-weighted CDI, city-level scatter, population-weighted CDI distribution and a sortable summary table.
- About / map / scatter help modals explaining the methodology.
- Bilingual UI (EN / IT) toggled from the header.
- Mobile responsive layout with tabbed cartogram / scatter / info panels.
data/
index.json ← city manifest (slug, name, center, zoom)
<city-slug>/
hexes.geojson ← hexagonal polygons + properties.id
cdi.csv ← hexagon_id, o_score_pt, o_score_car, CDI, population, …
The viewer joins on properties.id (GeoJSON) ⇄ hexagon_id (CSV) at load
time. To add a city, drop its folder under data/ and add an entry to
data/index.json. The landing page automatically detects which cities have
bundled data.
Campanelli B., Marzolla F., Bruno M., Melo H. P. M., Loreto V. (2026). Car Dependency in Urban Accessibility. arXiv:2604.01019