A moving measurement laboratory
The purpose is to turn a high-speed run into maintenance decisions. Sensor readings are processed aboard, and track crews use the results to locate poor geometry and compare conditions before and after work.
Shinkansen
923 · Doctor Yellow · T4 / T5
Look closer
What stands out in the nose profile?
先頭形状
Inspection train. A 700-series-derived broad bill.
jr-central.co.jpInspection train. A 700-series-derived broad bill.
JR Central’s T4 ended inspection runs in January 2025. JR West plans to end T5 inspections in January 2027 and withholds the inspection timetable.
Engineering details
923 type · JR West T5
| Formation | 7 cars |
|---|---|
| Base design | 700 series |
| Built | 2005 |
| Inspection-train maximum speed | 270 km/h |
Technical sources · 2026-11-07
- ワタシたちの解体新書 ドクターイエロー · JR西日本 · — · T5編成 基本DATA
Inside the engineering
923 inspection work; T5 identity and JR Central-group track-measurement account
| Electrical measurements | Overhead equipment, ATC signals and train-radio reception 1 |
|---|---|
| Track data processing | Underfloor sensors; real-time on-board waveform display |
| Maintenance handoff | Urgent findings relayed immediately; routine data sent by that evening |
Technical sources and page references
- ワタシたちの解体新書 ドクターイエロー
JR西日本 · T5 basic data and description of measurement targets - ドクターイエロー｜線路の状態を診る
日本機械保線（JR東海グループ） · 270km/hの高速走行で検測・ドクターイエロー検測室では
Inside the train
JR West’s seven-car T5 is a moving workplace. Instruments check overhead electrical equipment, track geometry, ATC signals and train radio reception during a run. A passenger reservation chart would miss what this interior was designed to do.
JR西日本 · ドクターイエロー T5編成 · 基本DATA ·Year introduced · 2001 T4 · 検測 / inspection
Did both 923 sets retire in January 2025?
JR Central’s T4 made its last inspection run on 29 January 2025. JR West’s T5 continued the Tokyo–Hakata inspection, including the Tōkaidō section east of Shin-Osaka. As of 7 November 2026, JR West plans to finish T5 inspections in January 2027.
ドクターイエロー（T4編成）部品オークション・車両解説 · ドクターイエロー（Ｔ４編成）引退に伴うイベント等の実施について · 1 · 500系新幹線＆「ドクターイエロー」Ｔ５編成の引退について · 1Can I look up T5’s last inspection in a timetable?
JR West says it will withhold inspection schedules, including the final inspection date. Separately announced events are the exception. The January 2027 notice gives a planned month; it makes no promise about a particular day or station.
500系新幹線＆「ドクターイエロー」Ｔ５編成の引退について · 1Why does a 923 resemble a 700 series, and what changed underneath?
The passenger 700 series supplied the starting design. To inspect at 270 km/h, the 923 adopted a 25 m track-measuring car running on two bogies. Laser measurement replaced the earlier system that determined track displacement from the physical positions of three bogies.
世界に誇る安全な新幹線を守ってきた「ドクターイエロー」の歩みを振り返る · ドクターイエロー（T4編成）部品オークション・車両解説What were the little roof domes on T4 for?
From the observation domes on cars 3 and 5, staff could watch the pantograph meet the contact wire. A camera at the observation position also fed pictures to the electrical inspection room in car 1. Car 4 handled a different signal entirely: its screens plotted track geometry as the train ran.
ドクターイエロー（T4編成）部品オークション・車両解説Why might T4 photographs show two different builders’ plates?
Check the car position first. JR Central identifies Hitachi as the builder of cars 1–3 and Nippon Sharyo for cars 4–7. All seven also carried JR Central’s own exterior plate. A photo of an ownership plate and a photo of a builder’s plate can therefore both be right for the very same car.
ドクターイエロー（T4編成）部品オークション・車両解説Sources and updates
Checked 2026-11-07