Google announced in its blog on August 25, 2009 that it was displaying crowdsourced congestion data from GPS enabled cell phones on Google maps.
". . . When you choose to enable Google Maps with My Location, your phone sends anonymous bits of data back to Google describing how fast you're moving. When we combine your speed with the speed of other phones on the road, across thousands of phones moving around a city at any given time, we can get a pretty good picture of live traffic conditions. We continuously combine this data and send it back to you for free in the Google Maps traffic layers. It takes almost zero effort on your part — just turn on Google Maps for mobile before starting your car — and the more people that participate, the better the resulting traffic reports get for everybody.
"This week we're expanding our traffic layer to cover all U.S. highways and arterials when data is available. We're able to do this thanks in no small part to the data contributed by our users. This is exactly the kind of technology that we love at Google because it's so easy for a single person to help out, but can be incredibly powerful when a lot of people use it together. Imagine if you knew the exact traffic speed on every road in the city — every intersection, backstreet and freeway on-ramp — and how that would affect the way you drive, help the environment and impact the way our government makes road planning decisions. This idea, which we geeks call 'crowdsourcing,' isn't new. Ever since GPS location started coming to mainstream devices, people have been thinking of ways to use it to figure out how fast the traffic is moving. But for us to really make it work, we had to solve problems of scale (because you can't get useful traffic results until you have a LOT of devices reporting their speeds) and privacy (because we don't want anybody to be able to analyze Google's traffic data to see the movement of a particular phone, even when that phone is completely anonymous)" (http://googleblog.blogspot.com/2009/08/bright-side-of-sitting-in-traffic.html, accessed 12-18-2011).