Using technology to thwart bike thieves

Penn junior Ben Perlman lost a bike locked, laced to his porch.
Penn junior Ben Perlman lost a bike locked, laced to his porch. (MELISSA DRIBBEN / Staff)
Posted: August 05, 2013

Ben Perlman knew how to lock up a bike.

Every night, the University of Pennsylvania junior said, he latched a U-lock onto the frame of his $400 Cannondale, laced a cable through the wheels, and secured it all to a fat wooden post on the porch of his off-campus house in West Philadelphia.

But the city's bike thieves are a determined lot. One morning 18 months ago, Perlman woke up to find it all gone.

Including the wooden post.

"Which, to me, was impressive," Perlman said. "The way I locked it . . . they would have had to carry the whole thing away."

A new study of police data has identified the hottest spots for bike theft in Philadelphia. And Perlman lives in the hottest one of all - University City around the Penn campus.

The close second and third winners of this dubious honor are Washington Square East and Rittenhouse Square.

This summer, six bicycles were stolen from Perlman's roommates at a house they share on the 4000 block of Walnut Street.

And peak bike-stealing season hasn't even kicked into gear.

Police data show that, every year in August and September, nearly 600 bicycle owners return to wherever they left their wheels to find hacked metal, amputated frames, or nothing at all.

In the last six years, more than 10,700 bicycles, with an aggregate value of $3.9 million, were reported stolen in Philadelphia, said Tyler Dahlberg, a graduate student from Clark University in Worcester, Mass.

Dahlberg, 28, is here for the summer on a fellowship sponsored by Azavea, a geospacial-analysis software-development company - they make data and maps to produce information in amazing ways.

His project will yield an interactive map that pinpoints where and when bicycle theft occurs.

As more people use bicycles to commute and for recreation, thefts have naturally increased, said Susan Dannenberg, policy fellow for the Bicycle Coalition of Greater Philadelphia, which proposed and helped design the project. The coalition will use the new map to warn the public where to exercise extra caution, she said, and perhaps to help retrieve a few purloined bikes.

Last year, an average of 160 were stolen each month, up from 135 a month in 2007. That's one every 4.5 hours.

Working at Azavea's hip, geekish offices decorated with cherry-red chairs and Bart Simpson dolls, Dahlberg projects graphs and maps onto a large computer screen on the wall. The one indicating monthly bike-theft totals looks like a cardiogram, a steady rhythm of highs in the summer and lows in the dead of winter.

One of Dahlberg's more unnerving discoveries is this: Once a bike has been stolen, the likelihood of another going missing in the next week from that exact location increases 260 percent. Even 90 days later, the risk is still 41 percent higher.

This could be because multiple bicycle owners tend to cluster in the same buildings, he said, or because there are bicycle racks in these locations.

Another graph - this one in concentric, multicolored circles - shows which days of the week are the riskiest.

"Mondays and Tuesdays," Dahlberg said, again noting that it was anyone's guess why. His job, he explained, is to identify the trends - not explain them.

The bicycle-riding community is developing other means of waging its counteroffensive against bike theft.

In the last two months, at least two bikes have been reunited with their owners with help from a new Facebook group - Philadelphia Stolen Bikes - and plainclothes officers from the Third Police District.

"It doesn't happen real often that bikes are recovered," said Officer Michael Duffy, who helped in both instances. His district, which covers most of South Philadelphia, has been encouraging residents for the last two years to register their bicycles with the police, filing photographs, serial numbers, frame size, and special identifying characteristics. Without those details, Duffy said, it is difficult to prove ownership.

"In the course of a few days, bikes can change hands several times," he said. So even if a bike is found, the thief who might have been charged with a felony may now be facing only a misdemeanor, receiving stolen property.

With the new Facebook group and other social media, the net for retrieving stolen bikes has widened considerably, said Duffy, who posts updates on Twitter (@ppdmikeduffy).

On June 16, Ryan Fiel reported to police that his $1,500 custom road bike with a yellow-and-red frame was missing. He posted the loss on the Facebook stolen-bikes page and quickly learned that it was for sale on Craigslist. The next day, he arranged to meet the seller. Police arrested the man, and Fiel got his bike back.

A woman, who asked that her name not be used, reported her $1,200 black-and-green Cannondale stolen in December. According to the police report, on July 8, a member of the Facebook group alerted her to a Craigslist listing in which a bike that looked like hers was for sale for $1,000.

She contacted the Third District police, who set up another successful sting operation.

In the last few weeks, since news of these incidents spread, several hundred new members have joined the Facebook group, which now has more than 1,500 and dozens of fresh postings of stolen bikes every day.

A sampling:

My beloved bike was stolen while I was working as a dog walker around front and Master streets, both the U lock and Cable lock were cut off of the bike and it was gone within minutes. It has a brown cup holder, a black basket . . .

Felt cruiser stolen off rack on 10th Street between Walnut and Chestnut on Tuesday, July 17th between 8 a.m. and 12:30 p.m. It has a custom rear rack (white) . . .

Stolen in West Philadelphia: Specialized Crosstrail Black and Silver, 2009 model, serial #: WUD096019096E, has black fenders, a black rear rack, an added water bottle holder and a stupid red basket tied on the rack . . .

No matter how sharp-eyed and well-coordinated the community becomes in its efforts to reunite owners with their bikes, said Dannenberg, the best strategy is to lock up your baby well.

"Some people are good with spatial relationships. Some are not," she said, so the Bicycle Coalition has posted a video on its website with thorough instructions on how to properly batten down.

For someone like Perlman, who has already been burned, no amount of hardware is going to give him confidence. He locks up his new Cannondale (which he won this year in a $10 raffle) in populated areas only for short periods of time. And at night?

"I'm not taking any more chances," he said. "I bring it inside."

Contact Melissa Dribben at 215-854-2590 or, or follow on Twitter @dribbenonphilly.

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