The Tech Behind Traffic Apps: How (Well) Do They Work? : All Tech Considered A host of apps aim to take the guesswork out of navigating traffic. We put their accuracy to the test in a daily commute. As varied as the options are, the future of mobile GPS may be more precise.

The Tech Behind Traffic Apps: How (Well) Do They Work?

  • Download
  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript


Today for All Tech, we ask, do traffic apps really help? Or, to be precise, did they really help me get to work any faster? Some confessions - I have a short commute from Arlington, Va., to NPR's headquarters, and while I won't admit to obsessive compulsive traffic jam evasion disorder, I do regard my commute as a daily technical challenge. So when my colleagues, All Tech editor Franklyn Cater and producer Rachel Rood, suggested that we take competing apps for a test drive, I agreed.

FRANKLYN CATER, BYLINE: Why don't you get Waze going?


SIEGEL: One ride, multiple free, downloadable apps. Franklin used INRIX on his phone.

CATER: So, right now, INRIX is saying it's going to take us 23 minutes.

SIEGEL: This ride is about 15 minutes in no traffic, but this was morning rush-hour. Rachel's phone had the longest forecast.

ROOD: Mine is saying that it's going to take 30 minutes to get there, and I'm using Waze.

SIEGEL: Waze is the Google-owned app that's enhanced by reports from motorists. Tap the phone to indicate where you spot an accident or a police officer. My Volkswagen navigation system was also on, and my phone was set to Apple Maps.

Well, mine says 22 minutes if I go by 23rd Street. Well, that's not the way I would ever thing of going in right row, but I'm game.

Note - we could do this because we had a carpool to handle the phones. We do not advocate driving while apping.

All right, well, let's see what the car's navigation system will tell me about where to go here. It says, manage congestions, so I'll have it do that.

GPS: (Through computer-generated voice) The route is being calculated.

SIEGEL: The first peculiarity of driving with so much high-tech assistance came up right away.

GPS: (Through computer-generated voice) Now turn right.

SIEGEL: My phone is telling me, as I leave my road here, to turn right and my...

GPS: (Through computer-generated voice) Turn left.

SIEGEL: ...Car - you can hear - is telling me to turn left, so I'm going to follow the phone just as a - for an experiment.

After almost 30 years of turning left out my road, I followed the three apps that told me to to turn right. One of them told me to make the next left, even though there was no left turn allowed at that time of day.

GPS: (Through computer-generated voice) Turn left now.

SIEGEL: And then we came to a light that has no left turn arrow and plenty of cars waiting to turn left, including mine.

So I would have avoided this. I don't know what my phone thinks it's doing.

We waited for the light to change and then to change again.

CATER: Do you think we'll even get through this light on this turn - on this green?

SIEGEL: No. No, I think this was a mistake by the app.

After that traffic light, the apps got me to the 14th Street Bridge over the Potomac without any problem. One of them, Waze, knew a clever bypass I sometimes use through a parking lot.

ROOD: My Waze app is very confused. It keeps changing routes.

CATER: We're literally going through a parking lot.

SIEGEL: I snake through city streets, neither helped nor hindered much by the carload of apps...

I'm not going to go to 9th street, no. You don't know what you're talking about.

...Until we were a few blocks from the office.

GPS: (Through computer generated voice) Watch out - accident reported ahead.

ROOD: A Waze reporter says there's a major accident right at North Capitol and K.

SIEGEL: Oh, no.

ROOD: Reported six minutes ago.

CATER: Everything looks green on INRIX here.

SIEGEL: Well, we'll be there in a minute, so we'll see.

If that intersection is blocked, I could be sentenced to 10 minutes circling NPR on one-way streets full of Washington drivers.

ROOD: But I don't see the major accident. Do you guys?

SIEGEL: No. I see no evidence of there having been a major accident.

And it was clear sailing for the last couple of blocks to NPR.

Morning. Well, here we are.

Took about 30 minutes - longer than most of the apps predicted. This wasn't a very scientific test of traffic apps, but it wasn't a very convincing one either. To better understand how all this works, we turned to an expert.

RAY RESENDES: I'm Ray Resendes with the Virginia Tech Transportation Institute.

SIEGEL: Virginia Tech does research with many traffic app companies. Resendes joined us for the same ride from my house the next morning, and that nonexistent accident at K Street from the day before was still fresh in my mind.

I mean, my frustrations is that sometimes when I hear a warning, even, you know, from the traffic report on the radio or an app, it's a little old. And on my commute, for information to be five minutes old, could be as well as an hour old, you know, if it's not there anymore.

RESENDES: Right. And you're going to have that frustration with almost any application you use because they're all using the same data.

SIEGEL: Back in the car, Resendes says most of the data is called probe data, gathered from the signals of cell phones as they move along streets. It also comes from government agencies.

RESENDES: The District Department of Transportation also has some instrumentation on this roadway. The gantry that we're coming up to - you can see some traffic cameras and sensors located on there.

SIEGEL: UPS trucks and other fleet vehicles carry sensors, too. All of that is aggregated and displayed on your phone or your dashboard - red lines for heavy traffic, green lines for light.

RESENDES: Now, Waze is - also gives you speeds, so the road that we're going on to - it says is four miles per hour, which looks pretty accurate.

SIEGEL: Well, this is the toughest lane - the right lane. Now, Ray, you're telling me that all of these devices - the accuracy of the GPS on them knows what road we're on, but not what lane we're in?

RESENDES: Right 'cause you're getting from meters of accuracy - to know what lane somebody's in, you have to know within a meter. And then, for a safety application, you actually need to know down to centimeters where you are in the lane, so to get those higher levels of accuracy, you need additional equipment, which is a system called differential GPS.

SIEGEL: That might explain why the backed-up exit at Massachusetts Avenue makes the whole roadway look red on an app, even when traffic is flowing freely past it in the left-hand lanes.

GPS: (Through computer-generated voice) Follow signs for I-395 North D Street - Northwest U South Senate...

SIEGEL: Which brings us to the future. Ray Resendes of Virginia Tech's Transportation Institute says it'll all work better when we get data directly from the cars themselves - smart cars that communicate with one another. And Tim Lomax shares that vision. He's a mobility analyst at Texas A&M's Transportation Institute.

TIM LOMAX: If the cars will talk to each other and apps, smartphones could be a part of that, but really, it's the cars talking to each other, you don't need a traffic signal. As you're approaching an intersection, your car essentially applies for clearance through the intersection with all the other cars, and it rolls through, and all the other cars know to avoid it. The apps are sort of the precursor to some of that because we're getting access to geographic location, real-time, very detailed point measurements.

SIEGEL: And while that future is a ways off, Tim Lomax says apps that customize information are here now. When I open my iPhone in the morning, it already says, sunny today, it's currently 68 degrees, right now it would take you about 21 minutes to drive to Washington.

LOMAX: The technology exists for you to wake up your iPhone, your Android and have it go look at your calendar to find out what your schedule looks like. What's the traffic look like? Is there a big special event on your quarter? Is the weather bad? You know, there's an awful lot more that we can do to customize the experience for travelers and get them out of what I think is really the case - people choose the same mode every day.

SIEGEL: Soon, perhaps, my app could reduce traffic by telling me, like my conscience, why not carpool it today or take the train or a bus instead of my car?

GPS: (Through computer-generated voice)You have reached the destination. The destination is to your right.

SIEGEL: (Laughter) It's actually to my left.

Copyright © 2015 NPR. All rights reserved. Visit our website terms of use and permissions pages at for further information.

NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.