Transparent method
How the Tokyo family base model works
Public facts stay public. Japan Answers’ original value is the schema, normalization, weights, load penalties, confidence labels and editorial synthesis that turn scattered network information into a reversible decision.
Version: Tokyo family base model 1.0 · 2026-08-24
The model does not predict travel time or crowding. It ranks six broad bases on a consistent 1–5 editorial scale and then applies the priorities entered in the selector.
Layer 1 · sourced facts
What comes from official public inputs
Airport access pages establish the operator corridors serving Tokyo. Rail network maps establish which line families meet each area. Official destination pages provide neighborhood orientation. These facts are credited; Japan Answers does not own them.
- Haneda Airport: train access — checked 2026-08-24
- Narita Airport: train access — checked 2026-08-24
- JR East: Tokyo rail network maps — checked 2026-08-24
- Tokyo Metro: network map — checked 2026-08-24
- GO TOKYO: Asakusa — checked 2026-08-24
- GO TOKYO: Shinjuku — checked 2026-08-24
- GO TOKYO: Tokyo Station and Marunouchi — checked 2026-08-24
Two rail map sites returned bot-protection responses to our automated check on the review date; their public URLs remain the cited operator references. Airport and listed GO TOKYO pages returned successfully. A blocked automated fetch is not evidence that a route or service is unavailable.
Layer 2 · normalized decisions
The six 1–5 dimensions
| Dimension | What 5 means | What it does not mean |
|---|---|---|
| Haneda / Narita arrival fit | The area is structurally well placed for that airport in the published network | A direct train at your arrival time |
| Station ease | Lower navigation burden relative to this six-area set | Step-free access from every platform to every hotel |
| East / west reach | Good fit for repeated days on that side of Tokyo | A measured minute-by-minute journey |
| Intercity launch | Useful access to long-distance departure patterns | Every intercity train leaves there |
| Evening ease | Useful food/services or a manageable local return pattern | A safety, nightlife or restaurant-quality rating |
Layer 3 · formula
Weights and penalties stay readable
The selector computes a weighted average of the relevant 1–5 scores, converts it to 100 points, then subtracts a physical-load penalty. Airport fit receives 1.4× weight. A chosen trip direction receives 2.5×; balanced trips weight east, west and intercity equally at 1.2×. Station ease receives 2.4× for low tolerance, 1.4× for medium and 0.7× for high.
Each large bag—and one additional stroller/mobility-load unit—creates a larger penalty at areas with lower station-ease scores. Groups above four receive a small additional complexity penalty. Scores are rounded only after the complete formula. The source function lives in src/lib/tokyo-base-score.mjs and is covered by mutation and invalid-input tests.
Judgment and uncertainty
Confidence is about the record, not your hotel
High confidence means the broad network role and decision tradeoff are well established across multiple official inputs. Medium confidence means service pattern or station geometry can change the practical result more easily. No confidence label covers a hotel’s room policy, elevator route or current price.
| Area | Confidence | Last checked | Known unknown that can reverse the result |
|---|---|---|---|
| Ueno | high | 2026-08-24 | The station still has multiple operators and exits. A hotel described as “Ueno” may sit on the opposite side from the route you expect to use. |
| Asakusa | medium | 2026-08-24 | “Asakusa Station” refers to separate operator facilities. A through-service shown on a network does not mean every departure is direct. |
| Tokyo Station / Marunouchi | high | 2026-08-24 | “Near Tokyo Station” is not a walking-time guarantee. Yaesu, Marunouchi and underground approaches create very different luggage routes. |
| Shinagawa | high | 2026-08-24 | The main station is broad and busy. Nearby properties can still involve crossings, elevated walkways or a long platform-to-lobby path. |
| Shinjuku | high | 2026-08-24 | Station side is decisive. A property on the wrong side can add confusing internal walks or force a street-level detour. |
| Ikebukuro | medium | 2026-08-24 | East and west exits lead to different daily lives. Airport convenience is not the main reason to choose this base. |
Version policy
When the model changes
A new version is required when an area, dimension, formula weight or penalty changes. Source-date refreshes without scoring changes can keep the same major version. We preserve unknowns rather than filling gaps with guessed fares, schedules or walking times.