Doctor Yellow  The trains have special equipment on board to monitor the condition of the track and overhead wire, including special instrumented bogies and observation blisters. 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 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 on the Tōkaidō Shinkansen).