3 replies to this topic

[Hans van der Maarel]

The idea is so simple it's amazing nobody thought of this before...

My province is tracking the daily traffic jams and the flow of traffic through cellphones. By triangulating the signal from different transmitters you can not only get a rather accurate position, but also, if you track it over time, speed. A high concentration of slow moving cellphones in what's supposed to be a major highway means traffic jam.

They use only one of the nation-wide cellphone networks and they don't ask for permission of the individual callers, which might be a breach of privacy.

[Martin Gamache]

Hans

How do they manage to distinguish between phones in slow moving cars and phones walking? It would work on major highways with few pedestrians, but in a dense urban area (think London or NYC) I think it would not be as useful.

In the US I think there is a law that obligates cell phone service providers to be able to locate any call. Many now have a built in GPS chip ( my 2+ yr old Verizon LG phone does)... This is much more accurate than the tower triangulation approach...but maybe too accurate for the privacy issues you refer to...

[Hans van der Maarel]

Martin,

I don't know, I was thinking the same thing actually. There was just a little blurb on a online news site with no more information than that. It was said that the service would be used to track traffic on highways, major roads outside urban areas but also major roads inside towns. Then again, in many cases you're faster on a bike than in a car in a urban morning rush hour and even when you're on foot you've got a pretty decent chance of winning... I don't think the tower triangulation trick is accurate enough to distinguish between a slow moving car on the road or a pedestrian on the sidewalk, especially if it's a rather narrow road.

[Rick Dey]

A similar process is being used here in the SF Bay Area. In this instance though they are tracking the movement of FasTrak toll transponders on the highways. Probably 25 to 50% of the vehicles on some of the commutes use them to pay bridge tolls. Antenna have been installed at intervals along the major freeways that note the time of a given transponder passing. Travel times and congestion are computed from that info. All data is purged daily and no information is available to correlate transponders with individual users. In the initial set-up of the system there were concerns of law enforcement using the data and privacy. The system operators have gone to pretty great lengths to protect privacy, including a statement that if it came down to the data being used for other purposes they would simply prefer to shut down the system. Transponder records from the toll plazas have been used for law enforcement though, thats a separate system.

The info is available at http://www.511.org/ Not the slickest looking stuff, but functional.