The Department of Homeland Security has deployed a mobile X-ray truck here in an experimental program of peeking into the unoccupied cars of drivers waiting to board the ferry to Delaware.
The program, which began a testing period Thursday, uses a van that previously has been deployed in border cargo searches to take X-ray pictures of parked cars. The low dosage X-ray shows any organic material, including explosives and drugs, as a dense white mass on a computer screen, while steel and other materials appear in ghostly outline.
The van snaps pictures as it moves along a line of cars at the pace of a stroll, but the manufacturer says the unit can scan when moving at up to six miles per hour.
Federal officials said that because the scans would be voluntary, no privacy issues were involved. Edward L. Barocas, legal director for the American Civil Liberties Union of New Jersey, said he could not discuss the new surveillance program in detail until he became familiar with it, but said drivers generally have an expectation of privacy for those parts of their cars that are not visible to those outside.
He said the United States Supreme Court ruled in 2001 that it was illegal for authorities to search homes from outside using infrared scanning without a search warrant, but also noted, ''Obviously in border searches the government is given a much broader leeway than elsewhere.''
The cars scanned Thursday were rental cars used by government workers participating in a demonstration. It took less than a minute for the van to pass each car.
For now, the scan at the Cape May-Lewes Ferry will be voluntary, said Carol DiBattiste, deputy director of the Transportation Security Administration, which is under the Department of Homeland Security. Drivers who agree to have their car scanned during the 30-day testing phase will be asked to leave their cars, and to remove pets. The X-ray dosage is not harmful to photographic film, food or any other contents of the car, officials said.
Ms. DiBattiste said a decision to make the inspections compulsory had not been made. She said the X-ray unit eventually could be deployed to scan cars in any setting.
''Right now our focus is on ferries,'' Ms. DiBattiste said, ''but eventually this technology could be used for any vehicle security information.'' Ms. DiBattiste said the ferry vehicle scanning program was part of an effort to use advanced technology in the government's crime prevention and antiterror efforts, including iris scans and fingerprint readers to confirm the identities of workers at airports and other security areas.
The $600 X-ray unit is called the Z Backscatter Van, and was developed and built by American Science & Engineering Inc. of Billerica, Mass. The company says about 60 vans have been sold to various governments.