Doctor Yellow (Japanese: ドクターイエロー, Hepburn: Dokutā Ierō) is the nickname for the high-speed test trains that are used on the Tokaido Shinkansen and San'yō Shinkansen. On Shinkansen lines operated by the East Japan Railway Company (JR East), there is an equivalent called East i. The trains have special equipment on board to monitor the condition of the track and overhead wire, including special instrumented bogies and observation blisters.^[1][2]

The "Doctor" part of the name is from their test and diagnostic function, and the "Yellow" part comes from the bright yellow color they are all painted. Some have a blue waistline stripe, some a green one. The original color scheme of yellow with a blue stripe (applied to the Class 921 track-recording cars) was created by reversing the colors (blue with yellow stripe) used on 1,067 mm (3 ft 6 in) narrow-gauge track-recording cars.

In build and appearance, they are very similar to production, passenger carrying Shinkansen trains, and line inspection is carried out at full line speed (i.e. up to 270 km/h or 168 mph on the Tōkaidō Shinkansen).

Because the schedule for this train is not made public, witnessing it in action is a case of chance. As a result, seeing Doctor Yellow in operation is believed to bring the viewer good luck.^[3]

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  • 921-1: Built in 1962 (initially numbered 4001), and withdrawn in 1980.
  • 921-2: Converted in 1964 from former MaRoNeFu 29-11 sleeping car, and withdrawn in 1976.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  • 922-0 (Set T1): 4-car set converted in 1964 from the prototype set (class 1000 Set B) built in 1961, and withdrawn in 1976.
  • 922-10 (Set T2): 7-car set owned by JR Central. Built in 1974 and withdrawn in 2001.
  • 922-20 (Set T3): 7-car set owned by JR West. Built in 1979 and withdrawn in 2005.
• 700 series type (Yellow with blue stripe):
  • 923 (Set T4): 7-car set owned by JR Central. Delivered in 2000.
  • 923-3000 (Set T5): 7-car set owned by JR West. Delivered in 2005.

• 
  JR Central Class 922 set T2, October 1998
• 
  JR West Class 922 set T3, October 2004
• 
  JR Central Class 923 set T4, April 2013
• 
  JR West Class 923 set T5, July 2008

For Tōhoku, Jōetsu, Hokuriku, Yamagata, and Akita Shinkansen

• 200 series type (Yellow with green stripe):
  • 925/0 (Set S1): 7-car set owned by JR East. Delivered in 1979 and withdrawn in 2001.
  • 925/10 (Set S2): 7-car set owned by JR East. Converted from former Class 962 test train in 1982 and withdrawn in 2002.
• E3 series type (White with red stripe)
  • E926 (Set S51): "East i" 6-car set owned by JR East. Delivered in August 2001.

• 
  Class 925 set S1, 1987
• 
  Class 925-10 set S2, September 2002
• 
  E926 East i train, August 2020

Interior (Class 923)

Source:^[4]

• 
  Interior of car number 1 used to inspect signalling, communications and power
• 
  Interior of car number 2 used to measure electricity
• 
  Observation window in car number 3
• 
  Seats in car number 5
• 
  A meeting table in car number 6

Preserved examples

• 922-26 (ex-set T3, built 1979 by Hitachi) at SCMaglev and Railway Park, Nagoya, since March 2011^[5]

In popular culture