thumb|300px|JR Central's Class 923 "Doctor Yellow" set T4 on the Tōkaidō Shinkansen, September 2021
thumb|300px|JR West's Class 923 "Doctor Yellow" set T5 on the Sanyo Shinkansen, December 2009
is the nickname for a series of high-speed maintenance of way and track geometry trainsets used on JR Central's Tokaido Shinkansen and JR West's San'yō Shinkansen lines. The trains have special equipment on board to monitor the condition of the track and overhead wires, including special instrumented bogies and observation blisters. Line inspection is carried out at full speed, up to on the Tōkaidō Shinkansen and on the Sanyō Shinkansen. Railfans have set up websites and social media accounts to predict Doctor Yellow's arrival dates and times at stations along the route.
On 13 June 2024, JR Central announced that they would terminate use of Doctor Yellow trains on the Tōkaidō Shinkansen line in January 2025, with plans for farewell events – including commemorative train rides, displays, and souvenirs – to be announced at a later date.
List of Doctor Yellow trains past and present
For Tōkaidō and Sanyō Shinkansen
- Non-powered track recording cars (Yellow with blue stripe):
- 921-1: Built in 1962 (initially numbered 4001), and retired in 1980.
- 921-2: Converted in 1964 from former MaRoNeFu 29-11 sleeping car, and retired in 1976.
- 0 series type (Yellow with blue stripe):
- 922-0 (Set T1): 4-car set converted in 1964 from the prototype set (class 1000 Set B) built in 1961, and retired in 1976.
- 922-10 (Set T2): 7-car set owned by JR Central. Built in 1974 and retired in 2001.
- 922-20 (Set T3): 7-car set owned by JR West. Built in 1979 and retired in 2005.
- 700 series type (Yellow with blue stripe):
- 923 (Set T4): 7-car set owned by JR Central. Delivered in 2000. Retired on 29 January 2025.
- 923-3000 (Set T5): 7-car set owned by JR West. Delivered in 2005. To be retired in 2027.
<gallery class=center>
File:Dr.yellow1号車.JPG|Interior of car number 1 used to inspect signalling, communications and power
File:Dr.yellow2号車.JPG|Interior of car number 2 used to measure electricity
File:Dr.yellow3号車.jpg|Observation window in car number 3
File:Dr.yellow5号車.JPG|Seats in car number 5
File:Dr.yellow6号車.JPG|A meeting table in car number 6
</gallery>
Retirement from JR Central Services
thumb|The wording on the windows of set T4 saying "ありがとうT4" (Thank You T4) on 28 January 2025, one day before its retirement
On January 29, 2025, the T4 set Doctor Yellow departed from Tokyo Station bound for Hakata Station for its final run on the Tokaido Shinkansen before its retirement, and for this special occasion, "ありがとうT4"(Thank You T4) was decorated on its windows. After Doctor Yellow's retirement, JR Central plans to use N700S Series units equipped with inspection tools to patrol its tracks.
Preserved examples
Currently, two examples of the Doctor Yellow units have been preserved:
thumb|Preserved Doctor Yellow car 922-26 inside the [[SCMaglev and Railway Park, March 2011]]
- 922-26 (ex-set T3, built 1979 by Hitachi) at SCMaglev and Railway Park, Nagoya, since March 2011. It is due to be moved to Hakusan, Ishikawa Prefecture sometime after May 2025.
- T4 (debuted in 2001) at SCMaglev and Railway Park, Nagoya
See also
- Comprehensive Inspection Train, used to evaluate the condition of the China Railway High-speed network.
- New Measurement Train, the British equivalent of Doctor Yellow, used to assess the condition of track
- TGV Iris 320, the French counterpart of Doctor Yellow, used to monitor the condition of the French tracks (mainly the high-speed railways LGV) used by high-speed trains, as well as High Speed 1 in the United Kingdom.