This is a very interesting report. It was based on anonymized tracking of cars with cell phone GPS signals to better understand the whole traffic network of the Bay Area. Identifying choke points for traffic led to a policy proposal.
"John Goodwin, a spokesman for the Metropolitan Transportation Commission, the region's transportation planning agency, says the best way to spread out traffic coming from these neighborhoods is to install metering lights at their freeway onramps, which spaces out the traffic to help both those drivers and everyone else get to their destinations quicker. Though many important Bay Area freeways already have metering lights, such as Interstate 280 in the South Bay and Interstate 680 in the East Bay, others don't."
The Twin Cities metropolitan area, where I live, was the first place in the United States to gain special federal permission to put on-ramp metered signal lights on federal Interstate Highways used heavily by commuters. They empirically help a lot in smoothing traffic. One reason we know that is that for a while a doofus state legislator shut down the freeway metered ramp program, until traffic here became so unbearable that the meters were put back in use. I have heard from friends who travel here from other parts of the country that the ramp meters (implemented as red-yellow-green traffic signals just before a car gets onto the freeway) are confusing to people who usually drive where on-ramps are just unimpeded paths onto the freeway. But they definitely speed up traffic.
The Twin Cities has one federal highway, Interstate 394, with a pair of reversible lanes, usually eastbound (into Minneapolis from the suburbs where I live) in the morning, and westbound (out of the city into the suburbs) in the evenings. That helps with rush hour commuter traffic, except that a lot of cars are eastbound for evening appointments even as commuters are leaving the city, so the reversal of lanes still leaves the regular, nonreversible lanes badly congested each evening. I wonder if a traffic study like the one reported in the interesting article submitted here could identify how to smooth out the traffic problems we still have here.
I'm currently making regular morning and evening roundtrips on I-395 near DC. My northbound segment in the morning is in the same direction as most traffic (into the city), and the entrance is metered. When I do that same segment in the evening, it's the less traveled direction, and there is no metering. This is interesting because the evening drive is often just as slow as the morning drive, even though there's less traffic, something I blame entirely on the lack of entrance metering.
For those of you who want to read a bit more about the twin cities traffic metering program there's an entertaining chapter in Numbers Rule Your World that goes through the history and (very lightly) the stats behind it. http://junkcharts.typepad.com/numbersruleyourworld/
We do have metering lights (mostly just red and green, one car per cycle) on most of the on ramps in the Bay Area, but a lot of them do not get turned on, even when the freeway is congested and those that do turn on tend to turn off at the end of the official high traffic time, instead of at the end of high traffic (although they usually are adaptive to unscheduled low traffic).
In the South Bay Area, there is also usually a major shortage of space to queue behind a traffic meter or to allow for acceleration after a meter. CalTrans knows how to properly design freeways, they do it in Southern California, but up here, they don't show it.
Those damn lights are terrible. We have them in Auckland where one authority controls motorway a (freeway) an another the local roads. The lights cause banking up at on ramps, blocking local roads. The motorway flow is improved, sure, but local single lane roads become impassable for hours. The lights just shift the problem here in Auckland.
That's an annoying aspect of trying to retrofit old roads with new tech. Roads designed for ramp metering (in Australia at least) have much longer ramps, both before and after the signal (enough space after for the car to accelerate to the speed of the motorway from being stopped, and before to stop the queue clogging surface streets).
But, it could also be a problem with the algorithm they use. The more simple algorithms generally don't take queue length into account, but ALINEA/HERO, which we use in Victoria has queue control.
The lights just shift the problem here in Auckland.
This is exactly their intention, and it's exactly what it does in the Minneapolis area -- it adds a natural saturation point to every onramp, eventually leading to lots of traffic simply using surface roads.
If it was anonymized, they could in theory release the data, right? However the article states "all the data gathered in the study will be kept confidential". Don't these 2 statements contradict each other? Why would they need to keep anonymous data confidential?
The two statements are consistent. In order to do the analysis they need to keep track of the full paths that the individual drivers make. Given the paths, particularly over a period of time, it is easy to identify individuals, even if you dont have their names to begin with.
Abstract. Many applications benefit from user location data, but lo- cation data raises privacy concerns. Anonymization can protect privacy, but identities can sometimes be inferred from supposedly anonymous data. This paper studies a new attack on the anonymity of location data. We show that if the approximate locations of an individual’s home and workplace can both be deduced from a location trace, then the median size of the individual’s anonymity set in the U.S. working population is 1, 21 and 34,980, for locations known at the granularity of a census block, census track and county respectively. The location data of people who live and work in different regions can be re-identified even more easily. Our results show that the threat of re-identification for location data is much greater when the individual’s home and work locations can both be deduced from the data. To preserve anonymity, we offer guidance for obfuscating location traces before they are disclosed.
Then it sounds like they have data tracking drivers even off the main roads: homes, driveways, small residential streets, parking lots, office buildings. IOW it sounds like they could have done a better job at anonymizing it by truncating driver paths that are off the main roads and highways to only keep data relevant to their study.
They study high traffic density, so by definition, irrelevant data is data where traffic is under a certain density, which would automatically exclude private areas (homes, driveways, etc).
Ah, unexplained downvotes on what I believe is a reasonable point I make...
At the very least, if data cannot be made anonymous, and can so easily be associated to persons, then this is an argument that they should have never collected it without my consent in the first place. This would be an invasion of my privacy.
There's a limit to how much such data can be truly anonymized, especially when it can be combined with other data sources.
Would you be ok with someone relating an "anonymized" database of fingerprints? Of sequenced human genomes? Of credit card transactions? Anonymization is tricky.
That's the problem AOL ran into when it released their anonymous web search data several years ago.
I think their hearts were in the right place, but it turned out, even though AOL had no interest in attaching real names, that there were enough artifacts in there that other people could. Especially if it spilled hot soup on AOL.
It is nontrivial to make data so anonymous NO ONE can deanonymize it. It's considerably easier to make data anonymous in a way that people acting in good faith to not try to deanonymize it won't realize who is who
It's surprisingly easy to de-anonymize an anonymized dataset. http://arstechnica.com/tech-policy/2009/09/your-secrets-live... Just because the researchers decided to keep their subject's privacy doesn't mean they should publish the data for any troll to play with.
The research did not care about identifying the culprits more than by where their starts and destinations and at which times and speeds they travel. Knowing the identity is rather useless to the research.
"John Goodwin, a spokesman for the Metropolitan Transportation Commission, the region's transportation planning agency, says the best way to spread out traffic coming from these neighborhoods is to install metering lights at their freeway onramps, which spaces out the traffic to help both those drivers and everyone else get to their destinations quicker. Though many important Bay Area freeways already have metering lights, such as Interstate 280 in the South Bay and Interstate 680 in the East Bay, others don't."
The Twin Cities metropolitan area, where I live, was the first place in the United States to gain special federal permission to put on-ramp metered signal lights on federal Interstate Highways used heavily by commuters. They empirically help a lot in smoothing traffic. One reason we know that is that for a while a doofus state legislator shut down the freeway metered ramp program, until traffic here became so unbearable that the meters were put back in use. I have heard from friends who travel here from other parts of the country that the ramp meters (implemented as red-yellow-green traffic signals just before a car gets onto the freeway) are confusing to people who usually drive where on-ramps are just unimpeded paths onto the freeway. But they definitely speed up traffic.
The Twin Cities has one federal highway, Interstate 394, with a pair of reversible lanes, usually eastbound (into Minneapolis from the suburbs where I live) in the morning, and westbound (out of the city into the suburbs) in the evenings. That helps with rush hour commuter traffic, except that a lot of cars are eastbound for evening appointments even as commuters are leaving the city, so the reversal of lanes still leaves the regular, nonreversible lanes badly congested each evening. I wonder if a traffic study like the one reported in the interesting article submitted here could identify how to smooth out the traffic problems we still have here.