Tiburon California Is Tracking Your Movements.

Your presence has been noted.

The posh and picturesque town that juts into San Francisco Bay is poised to do something unprecedented: use cameras to record the license plate number of every vehicle that crosses city limits.

Some residents describe the plan as a commonsense way to thwart thieves, most of whom come from out of town. Others see an electronic border gate and worry that the project will only reinforce Tiburon's image of exclusivity and snootiness.

"I personally don't see too much harm in it, because I have nothing to hide," commodities broker Paul Lambert, 64, said after a trip to Boardwalk Market in downtown Tiburon on a recent afternoon.

"Yet," he said, "it still has the taint of Big Brother."

Tiburon's camera idea is a marriage of technology, policing and distinct geography.

Situated on a peninsula, Tiburon's hillside homes and waterfront shops are accessible by only two roads, allowing police to point the special cameras known as license plate readers at every lane that leads into and out of the town of 8,800.

The readers, which use character recognition software, can compare plates to databases of cars that have been stolen or linked to crimes, then immediately notify police of matches, said Police Chief Michael Cronin.

If someone burglarized a Tiburon home at 3 a.m. one morning, he said, detectives could consult the devices and find out who came to town in the hours before - and who rolled out soon after.

'Very low-key'

"It's very low-key," said Town Manager Peggy Curran. "The whole point of license plates is that people can be identified by them."

If the Town Council gives final approval, Curran said, officials hope to install the readers on Tiburon Boulevard and Paradise Drive by late fall.

Tiburon plans to spend grant funds on the project and ask two other governments that could benefit from it to contribute to an expected price tag of $100,000 - the city of Belvedere, a bump of land on the southeastern edge of Tiburon, and Marin County.

Cronin called it a sound investment. He pointed to a frustrating twist in Tiburon crime: Residents feel so safe that they don't lock their cars and homes.

In all of 2007 and 2008, Tiburon recorded 196 thefts, 37 burglaries and a dozen stolen cars. The chief said every alleged thief who was arrested in those years was from outside Tiburon.

Finding suspects

Once the street cameras are installed, Cronin said, hunting a burglary suspect could be easier. "We'll look for a plate that came and went," he said. "That's going to give us a very short list to work on."

Detectives could then check to see if any of the cars has been linked with crimes in the past. Between 300 and 400 cars use Tiburon Boulevard to travel in or out of the town from midnight to 6 a.m. on weekdays.

"It's much more efficient than having an officer sit on the boulevard, watch passing cars and guess who might be a burglar," Cronin said.

Nicole Ozer, who directs policy on technology for the American Civil Liberties Union of Northern California, isn't as supportive. She called the cameras a "needle in a haystack" approach that may waste money, invade privacy and invite unfair profiling.

"To be under investigation simply because you entered or left Tiburon at a certain time is incredibly intrusive," Ozer said. "Innocent people should be able to go about their daily lives without being tracked and monitored."

City leaders promise to prevent abuses. Information on which cars enter and leave town will not be available to the public, they said, and will be erased within 60 days. Police officers will be granted access to the information only during an investigation.

License plate readers have exploded in popularity in recent years, but Tiburon would be one of the first to mount them at fixed locations - and perhaps the very first to record every car coming or going.

California Highway Patrol officials have put the readers on 18 cruisers and at four fixed locations. CHP officers have seen a huge increase in recoveries of stolen cars since the devices were installed starting in August 2005, the agency said.

Devices help CHP

Through December, officials said, the CHP had used the devices to recover 1,739 cars and arrest 675 people.

San Francisco gave the devices to police as well as parking control officers, allowing them to track cars parked for too long in one spot. Some cities use the cameras to assess anti-congestion tolls on motorists, while casino bosses get an alert when a high roller - or a cheater - pulls in.

Outside Tiburon's Boardwalk Market, where a flyer in the window offered a $2,000 reward for the return of a stolen Pomeranian, residents seemed split on the plan.

Robin Pryor, 66, of Belvedere said the most important issue was whether the cameras made people safer.

"It's just like locking your door," Pryor said. "If they have reason for it to bother them, they shouldn't be coming in."

But Fred Mayo, 62, who lives in Tiburon and owns a travel agency in Mill Valley, said the cameras would invade privacy. "Where does it end?" Mayo asked.

He referred to the crime blotter in the local newspaper, which listed two incidents recently of kids tossing water balloons at cars, and noted, "It's not like Tiburon's a high-crime area."

E-mail Demian Bulwa at dbulwa@sfchronicle.com.