New TriMet buses are equipped with not just video cameras, but also with microphones that can be used to pick up conversations between passengers.
Officials say the recordings can be used to investigate complaints, crimes and crashes.
"You know if there's a he said, she said, you know. Or an interaction that sort of escalates. Or there's anything illegal or criminal. You've now captured not only the video, but the audio," said Mary Fetsch, TriMet Spokeswoman.
"In a way it's a good thing for safety but in a way I think it's kind of an invasion of privacy," said passenger Dawn Batwell.
There are signs on the buses alerting passengers that they will be recorded.