Google today announced that Google Maps can now display live traffic data for more roads. Until now, Google only showed data from major highways. That data came directly from local highway authorities, but now, Google will also tap into data it receives from GPS-enabled phones that use Google Maps with the My Location feature. As users move around a city, Google can see how well traffic is flowing along any road and will update its live traffic data accordingly.

We noticed that Google actually started displaying more traffic data for these roads a few weeks ago, but Google described the specifics of this new program in a blog post only today. To send data (which is anonymized) to Google, users only have to open Google Maps on their Android phone (like the T-Mobile MyTouch 3G) or Palm Pre (we are still trying to figure out if BlackBerry and Symbian users can contribute as well). For now, the iPhone's Maps application doesn't support traffic crowdsourcing. If you don't want your phone's location to be tracked with My Location anymore, Google offers an easy way to opt out.

Update: We just heard back from Google - here is the official statement about which phones will be able to contribute traffic data to Google Maps:

Google Maps products that include location services will make use of this information for traffic. This includes the downloadable Google Maps for Mobile product for mobile phones as well as the Google Maps application for Android phones. One exception is the maps functionality that Google provides for the iPhone - the iPhone does not provide any location data that is used for traffic crowdsourcing at this time.

Google is obviously aware of the potential privacy issues involved here, but according to Dave Barth, the product manager for Google Maps, Google will "find the start and end points of every trip and permanently delete that data so that even Google ceases to have access to it." This way, nobody can find out where a car actually came from.

According to Google, enough users use these phones to make this project feasible. In my experience however, the data for these arterial roads isn't quite as trustworthy as the data for highways.

Overall, though, this is a great project and the more users are aware of it, the better the data will become. However, it is also worth noting that some GPS manufacturers have been using data from their users' GPS systems to crowdsource traffic data for years, though chances are that Google will be able to recruit more users and hence create a better experience for its users.