smoking car; car where smoking is allowed
Refers to a car (automobile) designated for smoking, such as a rental car or a private vehicle where smoking is permitted.
When I reserved a rental car, I chose a smoking car.
smoking carriage; smoking car (train)
Specifically a train carriage where smoking is allowed. This usage is becoming less common as smoking is increasingly banned on trains.
The old Shinkansen had a smoking car.
Compound of 喫煙 (smoking) and 車 (car/vehicle).