Associated Press

NEW YORK - The New York Police Department is working on a plan to track every car, truck or other vehicle entering Manhattan and screen them for radioactive materials and other terrorism threats.

The ambitious proposal, called Operation Sentinel, is being developed alongside a separate $90 million security initiative to tighten security at the World Trade Center site and elsewhere in lower Manhattan in response to the attacks of Sept. 11, 2001.

Police officials say Operation Sentinel would rely on license-plate readers, radiation detectors and closed-circuit cameras installed at the 16 bridges and four tunnels serving Manhattan. About a million vehicles drive onto the island daily.

The vehicle data - license plate numbers, radiological readings and photos - would be automatically analyzed by computers programmed with information about suspicious vehicles.

Police say the system could help them intercept would-be attackers.

There is no estimate yet of the cost, since Operation Sentinel is in just the planning phase.

The proposal already has raised red flags among civil rights advocates.

"We think that Operation Sentinel and a lot of the surveillance initiatives that the police are planning are an attack on our right to privacy here in New York," said Matt Faiella, a staff attorney for the New York Civil Liberties Union.