How does Google get traffic information for Google Maps?

by | May 16, 2010 08:00 PM ET
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Chris Pollette

Hello again, everyone. Welcome to Tech Stuff. My name is Chris Pollette, and I am an editor at www.HowStuffWorks.com. Sitting across from me as usual is senior writer, Jonathan Strickland.

Jonathan Strickland

And Leon is getting larger.

Chris Pollette

You've been threatening to do that for a while now, haven't you?

Jonathan Strickland

Yes, I have. Today's episode comes to us courtesy of a little listener mail. This listener mail comes from John. John says, "Hi, guys. I hope this email goes through. I didn't see a contact email on your web page, but I always hear you announce it at the end of your podcasts." It got through, John.

"First of all, I love listening to your podcast. You guys are great, and the subjects you discuss are also. Keep up the good work. My question is in regards to Google Maps traffic overlay. I usually check it before I leave from work in case I have to take an alternate route due to traffic problems.

"I'm wondering how Google can display how the relative speed is of a particular stretch of highway or road. Do they use cameras? Do they measure cell towers handing off phones? Do they rely on people calling in? Google seems to have a lot of public information gathered in one place, but I don't know how they got their real-time traffic data.

"If you've already done an article or podcast on this that I've missed, please direct me in the right direction. It would be great to hear an answer on the podcast, of course. I am really interested in the answer, so any way you can help would be appreciated. Keep up the great work. John."

Thanks, John.

Chris Pollette

You want to know the fascinating thing about that, John? They're getting it from you.

Jonathan Strickland

If you're using any kind of cell phone that happens to have a GPS receiver in it and also is using Google Maps with the My Location option turned on, you are contributing to the information that Google is using to generate those traffic overlays.

Chris Pollette

That's pretty cool. Well, it depends on how you look at it. You might be afraid, for example, that, "Wait a minute. So I have Google Maps for mobile turned on on my phone. I thought I was just checking out the traffic. You mean they're taking information from me?"

Google would actually say not to worry too much about that because they're not really taking any identifiable information from you. However, they are also taking pains to mix it in with other information taken from other customers, so don't worry so much. You're not being peeped upon, and they aren't following you on your way to work. Probably.

Jonathan Strickland

Right. let's give an overview of exactly what's going on here so that we can kind of discuss where the concerns come in and how Google has decided to try to meet those concerns. You raise a really good point Pollette.

There is a privacy issue here. What if you're not driving to work? What if you're driving to, say - I don't know. Maybe you're driving to the hospital, and you don't necessarily want people to know you have to go to the hospital. It's none of their business. It's your business. the thought of, "Does this mean there's some technology tracking my every move and that if someone were clever enough they could figure this out?" We'll get to that.

Generally what's going on when you're using these devices, the GPS receiver is what is identifying your location. Now, they can use cell towers to try and approximate your location, but that's usually not really that accurate. It's several dozen meters at best when you're talking about just cell towers whereas GPS, you're talking about a few hundred feet max.

Cell towers are not that great when you're looking at trying to figure out the traffic patterns of a particular area because if it's narrow enough, theoretically, you wouldn't be able to narrow it down to a specific street, especially if the city is laid out in a grid. You might be like, "Well, north/south travel seems to be going pretty well, but we aren't really sure which north/south street this guy is on." GPS gives you a much more specific location.

What happens is you've got this GPS system identifying where you are, and then your phone is contacting the cell towers on a pretty regular basis.

Chris Pollette

Yeah. As a matter of fact, this wouldn't work if you didn't have phone. If you had just a GPS receiver, you'd kind of be out of luck because I typical GPS receiver, just a plain old receiver, is not a transceiver. It's not sending information back to the satellites.

Jonathan Strickland

Right.

Chris Pollette

So Google gets the information. The GPS information is going to your phone, and your phone is contacting the cell towers. That's how Google is figuring out where you are.

Jonathan Strickland

Right. Think of your car as just that little dot if yo

u turn on the My Location. You know what I'm talking about. If you don't have it, here's what it looks like. You open up Google Maps. You turn on your My Locations. Then you get a little dot that indicates your specific location on the map. As you move around, the little dot moves around.

What happens is Google will track how fast you're moving along a particular route and extrapolate from that how traffic must be moving. This is not really useful unless Google is able to do it with lots and lots of users.

Chris Pollette

Right. For example, you could be walking down the street and everybody else is moving quickly, so Google is saying, "Apparently traffic is flowing normally, and this other person is doing something else." You would be an anomaly in that case because all the other traffic moving down the street is moving much more quickly than you are, or maybe your car is broken down and you're pushing it down the street.

Jonathan Strickland

Right. So Google could ignore you in that case. If you were the only person in the area who happened to be using this, then Google's conclusion would be, "Wow. Traffic on this street has crawled to almost a standstill. Look at how slowly they're moving." Obviously these sort of systems are only useful if lots of people are already participating. You can't just kind of go right out of the gate with accurate travel information. You really do need lots of different participants.

Google will look at the big picture, and the traffic overlay just gives you an indication of how fast traffic is moving along any individual streets.

Google is not the only company to take this approach. In fact, there was another company that some people in the tech industry were really excited about. They were producing GPS units that seemed really innovative and used this kind of feature where customers who used that GPS unit were contributing to the overall information about the city's traffic.

Chris Pollette

Yes. I was actually one of those people because I saw the company's technology at CES 2008. I was thinking how cool it was that they had a way to identify the businesses around where you were and give you an idea of what was going on because the information from the GPS receiver was blended with internet, and you got sort of an augmented reality effect.

Jonathan Strickland

I assume we're talking about the same company. Let's make sure. Dash?

Chris Pollette

Yep.

Jonathan Strickland

Excellent, well. Oh my gosh, listeners. You just got to hear a Renaissance Festival slipup. I said, "Excellent, well." Oh, man. I've already been working there for a few weeks, just in case you guys were wondering, and it is starting to seep into my normal speech. Feel free to write in and chastise me for doing a festivalism because I can't believe I did that. Anyway. Blooper reel.

These two systems work very similarly. You've got a centralized computing system that is collating all this data and then sending it back to the individual units, but the individual units themselves is what is contributing to the data. It's this interesting circular system.

Again, let's talk about why you need a lot of people. It's not just for the accuracy. It's also for privacy. Imagine that Google institutes this and there's only one person out there who happens to have the phone that does this. This is obviously just a ridiculous example, but let's say that Pollette is the only person in the world - or at least the only person in Atlanta - who has one of these phones, and Google has already turned on the system. That would mean the system would become not a traffic system but a "Hey, where the heck is Pollette now" system.

Chris Pollette

In case you're wondering, I'm the one wearing the red and white striped shirt and the toboggan.

Jonathan Strickland

He's also carrying a cane.

Chris Pollette

Yeah.

Jonathan Strickland

Anyway, that's why you need lots and lots of people. If you don't have a lot of people, it actually is possible to figure out, "Oh, this has to be so-and-so because he lives in that part of town. Look, where's he going? Oh my gosh."

Another thing Google does to try to minimize any chance that people would be able to identify a specific individual based upon traffic patterns is they will erase the original and destination of any trip. What they're looking at is they're just trying to figure out the speed of traffic along any particular route. They're not interested in the starting point or the finishing point, which is kind of interesting.

That's Google's approach. They're saying, "We understand your privacy concerns," which is weird for Google. They don't always seem to be really all that concerned. You can ask people who had to protest Street View, for example.

Chris Pollette

Or Buzz.

Jonathan Strickland

Or Buzz. That's another really good example about how Google sometimes seems to overlook the privacy issue. They really did think about it this time. As Pollette was talking about earlier, they also try to mix your data in with the data of other users so that there is no individualization there.

Really, that's the basics. It's really just data collection and incorporation into the map's application.

Chris Pollette

There may be another reason why Google erases the destination of the trip. Really, it's all about the journey.

Jonathan Strickland

Any way you want it, that's the way you need it. Any way you want it.

Chris Pollette

So.

Jonathan Strickland

Another reason you'd want it to be private, not just because of where you're coming from or where you're going to, which is obvious, let's say you don't happen to know that on a Friday night, Jonathan likes to go to the local gentleman's establishment and watch dancers. Jonathan doesn't. This is just an example. But let's say that he did do that. That would mean Jonathan would probably not want you to know that by looking at Google Maps.

That's not the only thing. The other reason you might not want this information to be identifiable to you, you might not want people to be able to tell that you're, I don't know, speeding down a main drag at a breakneck pace. You might not want folks to say, "I noticed on Google Maps last night that you were drag racing down Main Street." That would also be a reason why you'd want it to be privatized so that both the destination and the speed would be kind of hidden from other people.

Chris Pollette

Or, Jonathan, we noticed that you had the company car out last night, and you were speeding 45 miles per hour over the speed limit.

Jonathan Strickland

That would've been really awkward, seeing as how I don't drive.

Chris Pollette

I know. I was just using it as an example.

Jonathan Strickland

I'm sure I would end up in a pond somewhere, possibly a pool, some body of water.

Chris Pollette

I think a pond would be good for you.

Jonathan Strickland

It's inevitable.

Chris Pollette

How many movie references are we going to make in this podcast?

Jonathan Strickland

At least one more.

Chris Pollette

Probably. One of the cool things that I hadn't realized until I started doing some research on the traffic feature on Google's site is that Google is also keeping - and this is also a bit of a privacy concern , but I don't know that this is more so than anything else - Google is keeping track of historical traffic information.

If you are planning a trip next Thursday, say to go to the airport, and you want to know how traffic is on a Thursday morning going to the airport between 8:30 and 10:00 in the morning, you can look on Google and try to get a prediction of how traffic will be in the future.

Jonathan Strickland

It's going to clearly be over the roads because we'll all be driving flying cars.

Chris Pollette

Yes. I'm not going to say it. I came really close to making the other movie reference myself, but I'm just going to leave it out.

Jonathan Strickland

Where we're going, we don't need roads?

Chris Pollette

Yeah.

Jonathan Strickland

I told you we'd have at least one more.

Chris Pollette

That was the obvious one there. I think that's a very useful feature. It seems like you could easily plan a trip that way, something time sensitive like that especially is going to benefit from having that information. If you're not concerned about the privacy feature, there are lots of people who are going to be concerned about it regardless of what the company tells you.

Jonathan Strickland

Sure.

Chris Pollette

Then it can be useful to have that information and contribute to everyone else's overall knowledge of traffic patterns over the recent past few minutes as far as traffic is concerned, but also in terms of a historical sense.

Google is not the only one who does this.

Jonathan Strickland

No. Like we said, Dash does it as well. Some systems incorporate other elements as well, not just the user traffic or user experience, but they might have a report about a big event that's going on downtown and will automatically factor that in when routing your trip so that you don't end up going through a street that's closed off for that day. Some might even incorporate weather reports.

Chris Pollette

Yes.

Jonathan Strickland

The more advanced you get, the more information they'll bring in to factor these thing s in before you go on a trip, which is really kind of cool. A lot of them use a system completely different from Dash and Google.

Chris Pollette

Oh yes, definitely.

Jonathan Strickland

A lot of the GPS receivers that are not phones, they're just the GPS receiver, they'll also have a second receiver in there besides the GPS signal to accept traffic message channel signals. The traffic message channel is with ay of sending real-time traffic information out, usually over an FM signal, but you can also do it over satellite. You send that out to subscribers to your service, so various companies have their own specific frequencies. TomTom has its own frequency in various cities.

What'll happen is the company will send the real-time traffic information out, and so your GPS will update automatically. This way if there's a big wreck on one of the highways, it will come back with that information and give you the chance to reroute in the middle of a trip.

There are some problems with this technology. A lot of the companies that use it kind of have their system laid out on a grid. That's just the way the maps are, so when they have to mark down where an incident occurs, because it's a grid, it's not terribly precise. It's not like you can put a thumbtack exactly where the instant happened. You get an approximation.

Sometimes that approximation is wrong. Let's say there's an incident at an intersection. It may mean that one road leading into that intersections is affected, but the other three aren't. If the grid isn't exactly placed at the intersection in the proper way, it may show up as affecting the wrong road. Your route may say, "You can completely go this way. There's no problem here. It's unaffected," when it reality that's exactly where the problem is. It's not as precise as it needs to be. It's not foolproof, in other words.

Chris Pollette

Right. Meanwhile, you're cursing because you got stuck in traffic somewhere.

Jonathan Strickland

Right. You wanted to turn left, and the road is completely closed. You thought the road to the right was going to be closed, but it's fine. That's very irritating.

Chris Pollette

Going back to something you had said earlier incorporating weather and different events, of course, a system like that involves human interaction. It's not completely computerized.

TrafficCast is one of those companies that does that. They actually are the company that provides Yahoo with its service that you can see on the Yahoo Maps website.

One of the things that has improved about traffic information in general, I think, is that both systems, both Google and the TrafficCast system used on Yahoo and other sites is that they're starting to show information for arterial streets as well, not just the major highways.

TrafficCast's system is handled partially through human interaction, partially through other kinds of sensors. For example, they use the remote traffic microwave sensor, which tells whether or not you're making burritos in your car.

Jonathan Strickland

Wow.

Chris Pollette

No, sorry. Wrong notes.

Jonathan Strickland

I was really disappointed there.

Chris Pollette

No, not so much. it's a traffic sensor that uses microwave signals to figure out what's going on and can actually go across several lanes of traffic to identify the number of vehicles and their speed either from the side or from the front. As a matter of fact, it can monitor up to eight lanes, according to the information from TrafficCast's website.

It can get an idea of how fast you're moving. Those are stationary. It doesn't work the same way as having the GPS system through the Maps function in your phone. It doesn't get an idea of the same thing. They use a number of collection methods, including using GPS. It's kind of neat, too, that they're able to do that. They're also in contact with the local governments who have cameras and other systems set up so it can monito

r traffic. In general, I would say it's a lot easier to get an idea of what your commute is going to be like before you leave that it was just a few years ago. It seems to have come a long way in a very short period of time.

Jonathan Strickland

Right. They've got a much more comprehensive list of data collection sensors and methods. It's beyond just the users. That's a good thing. I remember when I first started getting into the working world, and I was looking at traffic reports and things like that. Really the only information you had came from cameras that were placed along certain highways. You could get a live look at what the traffic was like. You would get an approximation of the traffic. It would show up green, yellow, or red, but it was all the main highways. It was none of the surface streets. This is much more useful for most people, I would think, because it gives you a better glimpse of what traffic looks like throughout the entire neighborhood.

Chris Pollette

Yeah. Or you've got the other option, which is the traditional Traffic Copter 5 over the main thoroughfare. Was that on an episode of WKRP?

Jonathan Strickland

He just started pounding his own chest because the chopper was on the fritz?

Chris Pollette

Exactly.

Jonathan Strickland

Quite possible.

Chris Pollette

I don't think they had a traffic copter was the joke.

Jonathan Strickland

I zoned out. I had "Flight of the Valkyries" playing in the back of my head. Charlie don't surf. There's another one for you.

That pretty much wraps up all the information I have. This topic is fairly cut and dry, especially for a Tech Stuff topic.

Chris Pollette

It is, but it was kind of fascinating to me once I start looking at the other ways they measure traffic, and it explained some of those weird beige boxes they have on some of the poles along the side of the road. I'd always wondered what some of those are. I know there are other things too that they use, like air pollution detectors and things like that that you'll see on there.

The next time you go for a drive, some of the boxes you see with a little solar collector next to them may be using microwaves to check your car's speed and position out to help the traffic people identify whether the roads are clear or not.

Jonathan Strickland

It's neat stuff. I really do like the idea of crowd sourcing your traffic information. When you think about it, assuming that enough people are using it, that's going to give you probably the most accurate big-picture view of what traffic's like, how it's going in the city. Again, it'll depend entirely on whether people feel comfortable participating or not.

Chris Pollette

Yeah. I totally get that.

Jonathan Strickland

I guess that pretty much wraps that up. We'll go on to our second round of listener mail. This listener mail comes from Jaden. Jaden says, "Hey, Chris and Jon. I just listened to your cyborg episode and had to tell you about something I read. I read about a girl with some sort of degenerative eye condition. She got a mechanical eye where a normal eye would go. It had a camera and connected to her optic nerve. It was pretty cool. I just wanted to say that I love the podcast, and to keep them coming. I hoped you could maybe tell me about space shuttle tech or do a podcast on it. I'm only 13 and love tech, so I want to know everything about it. Please let me know. Thanks again. Jaden."

Well, Jaden, we do have the space shuttle technology on our list of topics, so it is on the list for us to tackle, along with about 150 other topics, but we are determined to hit them all eventually. As for the cybernetic eye, I've heard of an artist who wanted to have a camera implanted in a prosthetic eye. She is missing an eye, and she thought it would be an interesting way to capture images from her point of view, about as literally as possible.

Chris Pollette

Yeah.

Jonathan Strickland

And even programming it in such a way that she could control the method of capturing images by certain blinks, like if you blink twice, and suddenly it's captured still images instead of video, and that kind of thing. She had put out a call for engineers to try and help her with this, but from the last I checked, it still has not become a completed project. Also, this was not connecting to her optic nerve at all. It was merely to capture images, and then upload the images to a computer.

There's also a filmmaker who's trying to do something similar where he wants to have a camera implanted in his eye socket so he could shoot a film from his own point of view. Same sort of thing. Again, not connecting to his brain in any way. Just connecting to an outside recording device. Then his brain would eventually get around to seeing it when he watched the playback.

Interesting ideas. Not really cybernetic in the sense that it's not enhancing their own abilities. I

t's really just a new way to hold a camera, if you really want to think about it.

Chris Pollette

That's true.

Jonathan Strickland

Still kind of cool, and also scary. Come with me if you want to live.

All right, well that wraps up this discussion of Tech Stuff. If you have any questions, comments, you have some topics you'd like to suggest and have us add to the list of topics, write us. Our email address is TechStuff@HowStuffWorks.com. Chris and I will talk to you again really soon.

Chris Pollette

If you're a Tech Stuff fan, be sure to check us out on Twitter. TechStuffHSW is our handle, and you can also find us on Facebook at www.Facebook.com/techstuffhsw.

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