Google Maps added another nifty feature that will show live traffic conditions on arterial roads (non-highway roads) in selected cities. Google Maps will also show traffic patterns on main highways as well, helping see the least-trafficked route is for commute between two points.
To enable this feature, the user needs to zoom-in on the city and click the “Traffic” button in the upper-right corner of the map. This will give the traffic conditions of both arterial roads and highways. The colors correspond to the speed of traffic green is little to no traffic, yellow is medium congestion, red is heavy congestion, and red/black is stop-and-go traffic.
Google says that this feature can also be accessed on Google Maps for Mobile, which is particularly useful when trying to figure out the best route on the go. Google also shed a little bit of light as to how they crowdsource traffic info via Google Maps on mobile phones. On enabling Google Maps with My Location, the phone sends anonymous bits of data back to Google describing how fast the user is moving. When Google combines travelling speed with the speed of other phones on the road, across thousands of phones moving around a city at any given time, they can get an idea of traffic live conditions. They continuously combine this data and send it back to you for free in the Google Maps traffic layers.
Google assures users that they only use anonymous speed and location information to calculate traffic conditions, and only do so when the user has opted to enable location services on his or her phone.