The half-dozen people standing on the platforms for a few hours may not have stood out, but they were actually carrying sensors that tracked Metro passengers moving through Fort Totten Station based on signals emitted from the passengers\' pockets.

WASHINGTON — The half-dozen people standing on the platforms for a few hours may not have stood out, but they were actually carrying sensors that tracked Metro passengers moving through Fort Totten Station based on signals emitted from the passengers’ pockets.

The sensors detected Bluetooth signals emitted by cell phones and other electronics one morning about a month ago, with the goal of collecting information on passenger movements and crowding that could help with future planning.

Metro hopes the company’s data analysis, which is not yet complete, could help provide better information about how people move through the station, how long trains remain at the platform, how long passengers have to wait, and whether people prefer to transfer between the Green and Red lines at Fort Totten or at Gallery Place.

Right now, Metro’s main source of data is the fare system, which does not indicate which of several potential routes riders choose to take when there are several potential transfer points.

“We just had people stand with the equivalent of our sensors and collect data for maybe two-and-a-half hours during a morning rush hour at various places … on each platform and then the mezzanine between the two platforms,” says Stan Young, co-founder of the College Park Bluetooth-tracking company Traffax.

“The idea was could we see and observe [passengers] not only coming into the train station on the trains, but if they got off if we could observe them going down and catching the other train and leaving,” Young says.

Similar sensors from the company that was spun off from the University of Maryland in 2009 are used to detect traffic flow on roads across the region and the world. Traffax has sensors on a number of roads in the Washington area, including Interstate 270 and MD-355. They have also been deployed in more than 30 states and in Australia and Europe.

“A lot of people are worried about privacy,” Young says.

But “we can’t identify people, and, particularly, we can’t trace it back to any account. We just get an arbitrary identifier that we use to match up trip ends and get an idea of travel time and the quantity of people.”

If you’re worried about the information being collected, you can switch your phone’s Bluetooth off. Metro estimated before the test that one in 20 people would be carrying a device with the Bluetooth turned on.

The Traffax sensors usually track highway speeds, and the goal is now to prove that they can also be effective for tracking pedestrians, which requires more precision.

“We were interested in seeing if it produced meaningful data for pedestrians, and they were interested in whether it produced meaningful information that they could use for planning purposes,” Young says.

“Right now it’s used mainly for traffic applications, but we’ve also used the sensors for example to measure wait times at airport security checkpoints,” Traffax sales director Donna Nelson says.

“I actually took sensors to New York City and put them around the PATH station at the World Trade Center … and I was able to actually use the same concepts and technology to get an estimate of how people walked to and from this PATH station.”

A sensor by a bus stop, for example, may be able to detect how many people wait for the bus there, and for how long.

The sensors along Washington-area highways are non-descript gray boxes with the Bluetooth sensor, a GPS unit and a cellular data connection to provide real-time updates. They can detect any device with Bluetooth turned on from cell phones and navigation systems to the hands-free connections built in to many new cars.

“[Use of the technology] has been growing at a tremendous rate,” Nelson says.

“One is for these kinds of real-time monitoring applications that can drive the color coded maps on websites … but people also take the source data and use it as the basis of analysis.”

For example, this data can be used to predict traffic patterns in the future, Nelson says.

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