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Beating Traffic By Joining the Network
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A 2005 experiment by the Maryland Department of Transportation, for example, was scuttled after complaints that the cellphone data gathered from unwitting passersby to gauge traffic speeds could be used to track those cellphone users. That system measured speed by collecting information on how fast cellphone customers were moving between cell towers.
Other states, including Missouri and Georgia, have pursued or are pursuing similar plans. Georgia has deployed two services that use the cell-tower data to gauge traffic speeds on major roads in the state.
"We're not spying on anybody," said Paul Marshall, a spokesman for the Georgia Department of Transportation. "When we tell people about it, we say, 'We have a new way of getting traffic volume and speed information.' . . . They get paranoid when they hear it's cell data."
The cellphone data that the state receives, however, are "anonymized" -- that is, stripped of any identifying information such as the user's phone number -- and that allays most people's concerns, officials said.
The location information Dash gathers -- which by contrast comes from GPS coordinates, not cell-tower data -- will similarly be anonymized, company officials said.
"If the FBI comes in tomorrow and says, 'Where were you at 3 p.m. yesterday?' the honest answer will be, 'We don't know,' " Robert Acker, Dash's senior vice president of marketing, said.
The Dash device also offers a layer of what might be called domestic privacy: It allows users to delete recently searched-for destinations and services. Internally, company officials call that "the girlfriend program."
The thorniest technological challenge facing efforts like Dash's is how to turn the mountain of minute-by-minute location data from cars into a sensible map of traffic.
Simply translating a car's speed into traffic levels doesn't work. A car's slow movement might only reflect a slowpoke behind the wheel. A faster speed might only reflect an aggressive driver, or someone cruising the HOV lane. And unless they are properly accounted for, stoplights could look like traffic jams, which is why earlier efforts focused on highways alone. To address such problems, the Dash software looks for patterns in the data and throws out the outliers.
"It isn't enough to take the data and say this is the speed on the roadways," said Bryan Mistele, president of INRIX, a traffic-reporting company spun off by Microsoft that provides the baseline data in Dash's system. "You have to figure out what's going on."
The INRIX system started with more traditional methods of traffic detection -- embedded road sensors, radar -- but now largely relies on information received from commercial truck and taxi fleets, which account for more than 700,000 vehicles.
On a short test drive last week around Sunnyvale, the Dash unit displayed listings of nearby restaurants and gas stations. Out on the roads, it offered a combination of reasonably reliable traffic information based on average levels for that time of day and data from a scattering of other people testing the units.
