American Science & Engineering, a Billerica, Mass.-company, tells Forbes it has sold more than 500 ZBVs, or Z Backscatter Vans, to US and foreign governments. The mobile X-ray technology works by bouncing narrow X-ray streams off an object like a car and then analyzing the scatter rate of the returning rays. Operators can then locate less-dense objects that could be bodies or bombs.

The US Department of Defense has bought the most for war zone use, but now it appears that US law enforcement has also deployed the vans to search for bombs inside the US, according to Joe Reiss, a company spokesman.

On Tuesday, a counterterror operation snarled truck traffic on I-20 near Atlanta, where Department of Homeland Security teams used mobile X-ray technology to check the contents of truck trailers. Authorities said the inspections weren’t prompted by any specific threat.

“This really trips up the creep factor because it’s one of those things that you sort of intrinsically think the government shouldn’t be doing,” says Vermont-based privacy expert Frederick Lane, author of “American Privacy.” “But, legally, the issue is the boundary between the government’s legitimate security interest and privacy expectations we enjoy in our cars.”

AS&E’s Reiss counters privacy critics by pointing out that the ZBV scans don’t capture nearly as much detail of human bodies as their airport counterparts. The company’s marketing materials say that its “primary purpose is to image vehicles and their contents,” and that “the system cannot be used to identify an individual, or the race, sex or age of the person.”