NJ Transit is defending the collection of video and audio recordings of rail passengers, but officials say they are deciding whether to publicly release more details about the secretive surveillance operation.

The transportation agency has been criticized by some civil liberties groups and rail riders after reports this week revealed NJ Transit was monitoring and recording the conversations of light-rail passengers.

But NJ Transit pointed to instances of terrorism around the world, including last month's deadly attack on a Brussels airport and metro station, as the reason behind the monitoring, which the agency says they are well within their rights to do.

In a statement released Wednesday, NJ Transit spokeswoman Nancy Snyder also addressed some of the issues raised about access to the recordings and how long they would be kept.

"The New Jersey Transit Police Department is responsible for managing access to the recordings for limited investigative purposes," she said. "NJ Transit is reviewing what additional information about the operation of the system may be made public, including the location of cameras and the location and means of storage, while still protecting the system from physical destruction or compromise by criminals and those who would seek to undermine its effectiveness as a public safety tool."

Ed Barocas, legal director of the American Civil Liberties Union of New Jersey, told Townsquare Media this week that the audio recordings are an invasion of privacy and that the public should be entitled to know what the agency's policies are for maintaining, protecting and destroying the recordings.

Michael Phelan, of the New Jersey Commuters Action Network, which advocates for riders, said NJ Transit should be more concerned about overcrowded platforms and maintenance of trains and buses

"The agency's budget, energy and attention needs to be focused on improving day-to-day maintenance, service and safety — all of which present huge opportunities for improvement — rather than taking on the role of Big Brother over our conversations," he said Thursday.

Snyder said that rider feedback shows "our riders repeatedly asked NJT to improve security on the light rail system, and feedback from riders since the installation of the cameras has been overwhelmingly positive."

NJ Transit says it has no plans to put audio and video monitoring on its heavy rail lines.

NJ Transit's buses are equipped with audio and video surveillance systems but those have to either be activated by the driver or are activated by a collision, a spokesman said Tuesday.

Snyder said the NJ Transit Board of Directors approved the installation of cameras in 2011. The first systems were installed on the RiverLine in 2013, the Newark Light Rail last last year, and are now being installed on the Hudson-Bergen Light Rail.

While not answering specific questions, Snyder addressed some of the issues raised about access to the  recordings and how long they would be kept

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