Google on Wednesday rolled out a new feature on Google Maps that serves up instant traffic information for more than 30 major cities in the United States.

Using the new feature, commuters can see up-to-date traffic conditions in San Francisco, New York, Chicago, and other cities, to help them plan their routes around congested areas. Google follows in the footsteps of Microsoft and Yahoo, which also offer live traffic data through their mapping services.

Now people can search for a specific location by selecting the "traffic" button on Google Maps. When the traffic feature is enabled, major roads will be displayed on a map, marked by red, yellow, and green overlays that show the speed at which traffic is moving. Red means the traffic is stop-and-go, yellow means it's moving slowly, and green means the traffic is moving well.

Google launched a similar service for mobile devices in July.

The combination of a map and live traffic data is known as a mashup, formed by integrating multisourced applications or content into a single offering. Traffic mashups and thousands of others that include weather, city information, and even crime rates around the country are a growing phenomenon on the Web. More people are starting use mashups, and they're expected to hit the mainstream in the next two years.