You Already Own the Next Most Important Transportation Planning Tool

Your cell phone may provide the insight planners need to develop more efficient roads.

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Kyle Ward’s epiphany came the morning he realized the local traffic guy on TV had more information than he did.

"I was actually getting ready for work," says Ward, a transportation engineer with the Capital Area Metropolitan Planning Organization in Raleigh, North Carolina. “And I was looking at the TV, watching our local news traffic guy tell us about 'there’s congestion here, it’s good here.' I’m sitting there going 'he’s got way more sensors than the DOT does. How is he getting all this information?'"

In part, the answer is cell phones. From inside your pocket or your purse, your mobile is in constant communication with GPS satellites, cell phone towers and all of the apps that automatically update your gmail inbox and your Twitter feed. Your phone was never particularly designed for this purpose, but as it travels along with you, it has the potential to feed aggregated data about traffic congestion, commuting patterns and even mass travel behavior during a hurricane.

This is all information that someone like Ward wants to know. Until now, his MPO has obtained some of this data, maybe once a decade, through a "floating car survey." This involves rounding up a bunch of interns, whoever happens to be in the office, and sending them out to drive all over town. They're told to act – very scientifically – like a 50th percentile driver: Let half the cars pass you, the other half lag behind. Drive the route five or six times.

"You see where I’m going with this," Ward says.

This is a terrible idea. And it’s expensive. A floating car survey costs about $300,000 – and all this just to give transportation officials a sense of typical driving speeds. The MPO spends even more on household driver surveys to get a sense of where people live and work, and how they commute in between.

"This seems so wasteful," Ward says. “It just doesn’t make sense."

And so he actually called up the TV traffic guy. He learned, eventually, about a new breed of cell phone-tracking transportation planning tool, for which Raleigh became a national test case.

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Cy Smith jokes that he’s got an 11-year-old start-up. He started his company, AirSage, in 2000, but it has taken him this long to bridge the connection between the wireless industry and the transportation planning world, and to work through the visceral suspicion many people have at the thought of “tracking” cell phones.

"You can’t just go out and find a wireless/transportation expert," Smith says. "They don’t exist."

AirSage’s concept doesn’t rely on GPS, but rather on the network signaling data between the cell towers and your phone as you move across the network's coverage. This kind of tower triangulation can pinpoint your location within about 50 meters in a dense urban area. That’s close enough to measure travel speeds and conduct origin-destination studies. And the data collection doesn’t require that you have the GPS enabled on your phone.

AirSage’s main challenge, though, was obtaining this data from cell phone carriers to analyze and then use in studies for agencies like the Raleigh MPO. Cell phone carriers have figured out how to monetize just about everything. The industry makes a billion dollars just selling you ring tones. But it hadn’t yet occurred to anyone that this movement data was valuable, too.

"They don’t know a thing about transportation. They don’t know what the transportation community spends on trying to instrument the road network with their own technologies," Smith says. “And this is a network that they’ve already spent $300 billion on as an industry, to build out a network of towers, switches and electronic equipment. And quite frankly, what the infrastructure does is it looks at the movement of people. They use it for facilitating communications, and we want to use it to facilitate the movement of people, for transportation.”

Call it movement analytics. Eventually, Sprint signed on to work with AirSage, and a second national carrier is now on board (although the two haven't announced this publicly yet). Smith had to convince the carriers of the business case for using this data, but he also had to assuage the obvious concerns over personal privacy (as well as the concerns over any perception that personal privacy would be at risk).

AirSage only produces bulk, aggregated data, which is also the only kind of data that’s really of use to transportation planners.

"I haven’t met anybody yet that I can’t convince them it’s OK," Ward says. "And the reason why it’s OK is I never see an individual cell phone record. The only output I ever see is ‘from census tract 1 to census tract 2, we have an estimated 5,000 trips a day.'"

AirSage may be able count 50 cell phone sightings on a certain section of the I-440 corridor, with an average speed between all of them of 65 miles an hour. But no government official can see that it was your phone that was traveling 20 miles over the speed limit.

"I think people are rightly concerned that their data not be abused," Ward says. "I feel that way because I’ve got a cell phone. I don’t like the idea of anybody being able to track where I’m going."

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Ward’s MPO in North Carolina wound up contracting with AirSage to do an origin-destination study of travel patterns and to measure traffic speeds. Using cell phone data, that $300,000 floating car survey was essentially replaced for $25,000 – and with greater scale and accuracy. In the past, the MPO also collected origin-destination data by asking individual households to keep a log of their daily trips (a process obviously prone to human sloppiness). These surveys, which only produce results from about 5,000 households in a region of 1.6 million people, typically run between $700,000 and $1,000,000.

Those surveys provide a level of detail – did you take the bus or the car? were you going to school or the office? – that cell phone data can’t see. But AirSage’s Sprint database saw more than 600,000 individual phones pass through the Raleigh area over a 60-day period. AirSage takes those same cell phone sightings and isolates the census tracts where phones were most frequently reappearing at night (at home) and during the day (at work). That aggregated data can then be plugged into the models Ward uses to project population growth and transportation demand years into the future.

This is a bird’s eye view of all the common home-work travel pairs in Raleigh over this 60-day period (the most frequent trips are in black, the least frequent in purple):

The data doesn’t follow vehicles along precisely which roads they take from one point to the other, but Ward’s models can account for some of these probabilities. The macro trends do give a sense of how far people are commuting, where the common work nodes are, and where new roads or transit would serve the most people.

"We’ve now got the solutions to problems we didn’t know we had," Ward says. "Now we can think of them and figure them out."

That study cost the MPO only $50,000 (although, since it was a pilot project for AirSage, other agencies won’t get quite the same deal). Within the data, all kinds of patterns emerge. This, for instance, was one particularly dense destination north of town:

That nexus turns out to be the location of a Target and Sam’s Club commercial center (with each yellow line noting the number of extrapolated trips taken from various origins in this time frame). And here is a map focusing on trips to and from North Carolina State University:

Other uses to which this information could be put are vast. Carriers are collecting data all the time (and archiving it), and so officials in a coastal city, for example, could watch how residents reacted during a past hurricane to plan for an upcoming one. This data could even be used to answer a timeless politically divisive question: When Occupiers hold a protest, or Washington has an inauguration, or Glenn Beck stages a rally at the Lincoln Memorial, how many people really show up? Cell phone data could quash hours of cable-TV squabbling over just this question (and people other than pundits probably could use the answer, too).

"I personally am still struggling with ‘how do I get this all implemented in transportation?'" Ward says. "So I’ve only done some thinking in the shower about 'wow, I wonder what else we could do with this.' But I think the more people who realize what’s happening, you’ll get tons of people thinking about it, and lots of ideas will come out."

Photo credit: Mike Blake / Reuters

About the Author

  • Emily Badger is a former staff writer at CityLab. Her work has previously appeared in Pacific StandardGOODThe Christian Science Monitor, and The New York Times. She lives in the Washington, D.C. area.