Imperial car
Refers to a vehicle used by the Emperor or Imperial family, typically an automobile or railway carriage. Domain-specific term.
His Majesty the Emperor participated in the parade in the Imperial car.
The Imperial car is specially decorated.
車両 is a general term for rolling stock or vehicles, while 御料車 is exclusively for Imperial use.
Compound of 御料 (ごりょう, 'Imperial property') + 車 (しゃ, 'vehicle'). The prefix 御 (ご) is honorific.