Photo: Amy Osborne / Special To The Chronicle Photo: Amy Osborne / Special To The Chronicle Photo: Amy Osborne / Special To The Chronicle Photo: Amy Osborne / Special To The Chronicle Photo: Amy Osborne / Special To The Chronicle Photo: Amy Osborne / Special To The Chronicle Photo: Amy Osborne / Special To The Chronicle Photo: Amy Osborne / Special To The Chronicle

They’ve tried building fences. Hiring private security guards. Installing closed-circuit cameras around their homes to spot every passing car or suspicious-looking person.

And now, homeowners throughout the Bay Area and in other U.S. cities are turning to license plate readers as a next line of defense against property crime. The trend has helped generate a fertile market for companies that make the technology, though it also has raised concerns about privacy and led some academics to wonder whether people’s desire for protection has gone too far.

For Joseph Narvaez, a resident of Richmond’s Country Club Vista neighborhood — a community of single-family homes nestled by a golf course — a license plate recognition system seemed logical. He manages the one that his homeowners association purchased in March from an Atlanta startup called Flock Safety, now a leader in the home security sphere.

“We needed something to deter crime,” Narvaez said, describing the burglaries, car break-ins, doorstep package thefts and occasional street races that plague his neighborhood. He said crime has gone down since the association installed solar-powered cameras on black poles, clustering them at busy intersections and pumping the footage to an internet cloud that Narvaez can access with a password. Flock Safety charges $2,000 a year to install and maintain each camera, and provides signs to alert people they are being watched.

Photo: Amy Osborne / Special To The Chronicle

The popularity of these devices seemed to blossom overnight. When Flock Safety began a year ago, it had five employees and 10 customers. Since then, it has sold cameras and data-hosting packages to customers in 27 states, including homeowners associations in Richmond, Oakland, Fremont and along the Peninsula, as well as residents of San Francisco.

Perhaps it’s no surprise that these products found an audience in the tech-savvy Bay Area, where property crime is rife and license plate scanners have long been part of the urban landscape. The tony city of Piedmont blanketed its entrance points with plate-tracking cameras in 2013. And this year, the Alameda City Council set aside funding for a similar digital border patrol: 13 plate recognition systems to be placed over traffic lanes of bridges, underwater tubes and key intersections. Plate reading cameras roost atop gantries at the Bay Bridge toll plaza, and parking companies use the technology to determine when a space is empty.

So, private residential plate scanners might just be the next phase for a culture obsessed with surveillance. “The market reaction has been incredible,” said Flock Safety CEO Garrett Langley.

He has plenty of competition. Other outfits, such as Reconyx, sell similar consumer license plate reading technology. A company called OpenALPR makes commercial and open-source software that automatically recognizes plate numbers, and homeowners also have the option of buying similar surveillance products off the shelf.

Bigger companies in the market, such as Livermore’s Vigilant Solutions and the aerospace defense company Leonardo, sell primarily to law enforcement, though Vigilant has expanded its clientele to include hospitals, school campuses and corporate offices.

The major vendors have drawn scrutiny from lawyers and privacy experts at the American Civil Liberties Union and the Electronic Frontier Foundation of San Francisco, which published an extensive guide to license plate readers on its website. In one post, the foundation says that license plate data “can paint an intimate portrait of a driver’s life” or be used to identify “drivers who visit sensitive places such as health centers, immigration clinics, gun shops, union halls, protests, or centers of religious worship.”

Photo: Amy Osborne / Special To The Chronicle

Dave Maass, a senior investigative researcher at the foundation, said he is wary of the technology’s recent shift from police departments to property owners. What if someone uses these devices to stalk an ex-spouse or girlfriend, for example?

Or neighbors could band together and sell the data, said Albert Gidari, consulting director of privacy at Stanford Law School’s Center for Internet and Society. Minute information on comings and goings would allow businesses “to look at a whole community through the lens of these devices,” he said.

Flock Safety takes some steps to ensure privacy, such as deleting footage after 30 days and supplying an “opt-out” list for residents who don’t want to be recorded. Skeptics wonder whether it goes far enough.

Others see the plate-scanning gadgets as a natural byproduct of a society where cities are growing more demographically diverse and economic inequality is more pronounced. People with homes and things to protect are anxious to build walls around themselves — including digital walls, said Stephen Klineberg, a retired sociology professor at Rice University in Houston.

All of these social factors lead to a gnawing “sense of insecurity,” Klineberg said.

But the fears that drive people to purchase license plate readers are also grounded in data. San Francisco, for instance, had the highest per-capita property crime rate of any U.S. metropolis in 2017: 6,168 crimes per 100,000 people, according to the FBI. Oakland didn’t fare much better, with 6,142 burglaries, larcenies, car thefts and arson incidents for every 100,000 people.

Could these camera systems help law enforcement? Maybe.

“I see the point — that if you see something happen, you can rewind the tape,” said Barry Donelan, president of the Police Officers Association in Oakland, where some residents resort to using their own security apparatuses, including license plate readers. In Oakland, as in Richmond, the cameras and software function more as a deterrent to crime than a tool to catch perpetrators.

“We had a huge problem with people pulling over at the side of the road and dumping mattresses or construction materials,” said Cody Strub, treasurer of Hillcrest Estates homeowners association in the Oakland hills, near Skyline High School. The association bought three Flock Safety cameras in August, and Strub said the dumping stopped after that.

Even so, Donelan stressed that crime-stopping software is no substitute for human police officers.

“You can have all the technology you want. You can also put up a chain-link fence that’s 20 feet high,” Donelan said. “But ultimately you need the people to make the arrest.”

Rachel Swan is a San Francisco Chronicle staff writer. Email: rswan@sfchronicle.com Twitter: @rachelswan