Methodology, sources and credits
How travel times are calculated, where the data comes from, and what the map doesn't tell you.
Methodology
In Japanese cities, trains do most of the work: JR lines, private railways (in Tokyo: Tokyu, Odakyu, Keio, Seibu, Tobu, Keisei, Keikyu…) and, in the centre, subways. For each starting point, a shortest-path algorithm explores this whole network and works out how long it takes to reach every station, then every point on the map. Calculations run on our servers; your browser only receives the results. A journey is the sum of:
These simplifications make times comparable from one neighbourhood to another, but your actual journey may differ: long corridors in major stations, rapid and express trains that skip stations, changes between operators, which exit you take…
- Walking
- At 4.5 km/h, over the straight-line distance multiplied by 1.25 to account for detours.
- Platform access
- 1 minute to enter the station and reach the platform.
- Waiting
- Half the average interval between two trains, capped at 15 minutes. A line running every 4 minutes therefore costs 2 minutes of waiting on average.
- Transfer
- A 1.5-minute margin to change lines within the same station; between two stations of the same hub (for example the JR station and the subway station at Shinjuku or Ōtemachi), the actual walking time from one to the other.
- Timetables
- Official weekday timetables between 7 am and 8 pm. Intervals and running times are averaged over that period.
- Real time
- None: no delays, engineering works or crowding. Travel times are averages on paper.
Data sources
- ODPT (Public Transportation Open Data Center) network, lines, stations and timetables for JR, private railways and subways (Toei subway: 東京都交通局, CC BY 4.0)
- Mini Tokyo 3D additional line and station data
- © OpenStreetMap contributors geography, place names and base map
- OpenFreeMap base map vector tiles
- GSI, Geospatial Information Authority of Japan (国土地理院) address search and geographic data
- National Land Numerical Information (国土数値情報, MLIT) administrative boundaries and land data
Licences
Only the OpenStreetMap base map data falls under the Open Database License (ODbL) 1.0. Calculated results (travel times, simplified network) are derived from transport data subject to ODPT licences: they are shown only on this site and may not be redistributed.
The source code is not published: all rights reserved unless otherwise stated.
If you reuse the base map or the other open data listed above, follow their licences and credit their sources.
Credits
- Anthony Castrio: the NYC Transit Time Cartogram, where the idea of travel-time maps comes from.
- Jules Grandin: the Paris travel-time map.
The name
“Ikeruka” (行けるか) is the question you ask before heading out: 行ける (ikeru) means “can go”, and か (ka) turns it into a question. “Can I make it?” Ikeruka answers in minutes, by train and subway.
Accessibility statement
This site aims to conform to WCAG 2.2 level AA. It has not yet been independently audited, so at this stage it is partially conformant.
What is in place
- Full keyboard navigation, an always-visible focus indicator and a skip link to the main content.
- Contrast of at least 4.5:1 for text and 3:1 for interface components, in both light and dark themes.
- A colour scale readable by people with colour vision deficiencies, backed by time labels on the contour lines.
- A text alternative to the map: a list of stations sorted by travel time and a step-by-step route in text.
- Calculated travel times are announced to screen readers.
- Animations are reduced when your system asks for it.
- The language of every page is declared, including Japanese names.
Known limitations
The map remains a visual representation: its useful content is also provided as text, but the base map itself (streets, terrain) has no text equivalent.
Report a problem
If something prevents you from using the site, let us know at contact [at] ikeruka.com: we will look for a fix or provide the information in another format.