General term for a passenger on a train, bus, airplane, taxi, ship, etc. Neutral and widely used.
この電車には多くの乗客が乗っている。
There are many passengers on this train.
乗客の安全を第一に考えてください。
Please put passenger safety first.
The bus departed carrying a full load of passengers.
The taxi dropped the passenger off in front of the station.
Many passengers boarded the train.
The airline prioritizes passenger safety above all else.