Washington Post 
December 3, 2012
Around Washington, surveillance cameras are always watching. They peer from rooftops, lurk at intersections and even observe people riding a bus to work.
And on Montgomery County’s Ride On buses, the cameras do more than capture what they see. Many cameras also record what they hear, a little-known function that bothers civil liberties advocates. They see a creeping erosion of privacy in the growing use of audio recording technology on public transit.
The Maryland Transit Administration began audio recording in October on some buses in and around Baltimore and hopes to expand that to about half of the agency’s 700 buses by summer.
In San Francisco, buses and trains have both audio and video recording, with the audio devices always running. And in Atlanta, transit officials are adding video and audio recording to buses and will put them on trains next.