As if we needed another reason not to start up a conversation with the bus rider in the next seat:

is listening.

Oregon's largest transit agency has trumpeted the looks, comfort and fuel efficiency of its 55 new "3000 series" buses, including four hybrids.

But there's one feature on the new buses that has been kept pretty hush-hush: The on-board microphones.

With the 3000s, TriMet joins the list of public-transit agencies across the country that are quietly installing microphone-enabled surveillance systems on buses, creating worries about warrantless eavesdropping along the way.

The new 42-foot vehicles have multiple on-board microphones constantly recording everything from rider conversations to strange mechanical noises, just in case the audio needs to be used in crash investigations, customer-complaint reviews and criminal cases.

"Audio recording is a capability that came standard with the new buses," said TriMet spokeswoman Mary Fetsch. "It's not something special we ordered. But we are using it as part of the surveillance system."

In older buses, drivers can hit a button to activate a single microphone positioned at the front in emergencies, though drivers don't always exercise that option.

But the 3000 series buses –diesel versions carry a $440,691 price tag – manufactured by California-based Gillig feature six security cameras wired with always-recording mics. Eventually, every bus in the fleet is expected to have the technology.

Signs such as this one appear near the front of TriMet's new Gillig 3000 buses, letting riders know that their conversations can be recorded by the six cameras on board.

TriMet said state law allows the microphones because each bus has a prominently placed sign advising riders that they are being recorded near the front.

Buses are also public spaces where it could be argued there is not what the law calls "a reasonable expectation of privacy."

At the same time, Fetsch said, neither the video nor the audio will be routinely monitored. As always, she said, it will be "pulled" only when requested to review incidents. The audio, like the video, is also stored for a limited number of hours, typically 48 to 72.

But David Fidanque, executive director of

, said his organization is looking closely at the legalities. "Why should riders who are doing nothing wrong be subjected to having their conversations being recorded by TriMet as a condition of taking public transit?" Fidanque said. "This is an agency that wants to encourage people to get of their cars. This is a fine way to get them back in their cars."

The local ACLU has never liked TriMet's on-board video cameras. "But this is beyond that," Fidanque said. "There's a big difference between watching an image of two people having a conversation and hearing everything they're saying, anywhere on the bus."

Of course, anyone who regularly rides a bus will tell you that listening to many conversations, especially loud cell phone calls, would be tantamount to torture.

In December,

and TheDaily.com highlighted Eugene in a report on the growing number of cities installing microphones on buses, sometimes with funding help from the Department of Homeland Security.

Last year, for example, San Francisco's MUNI system used a $6 million Homeland Security grant to install an audio surveillance system on 357 buses and even the city's vintage trolley cars.

After the articles appeared online, the

posted lengthy response on its Facebook page, stating that "the investment in monitoring equipment" has helped provide safer and more efficient bus system for a decade. Eugene's bus microphones, which can be paired with video footage, are reportedly able to separate conversations from background noises such as wind, traffic, windshield wipers and engines.

"There is not spying," LTD stated.

In addition to rider assaults and accidents, the audio has helped the Eugene agency avoid fraudulent litigation and clear drivers of exaggerated complaints from riders.

"The beauty of having audio assistance in the process of investigating an incident," said Mark Johnson, LTD's operations director, "is that you can really tell what happened.

"There are complaints from people who say, 'The driver said this to me.' And we can pull up the audio and say, 'No, he actually said this.'"

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