It will depend if we are a passenger in a vehicle or are carrying passengers as to the interpretation.
If the former, we may feel that we are being carried along by circumstances, and have not really thought out our own way forward.
If the latter, we may have knowingly or inadvertently made ourselves responsible for other people in some way.
Travelling with one other passenger suggests we may be considering our relationship with that person or whatever they represent.
Also consult the individual entry for passenger.