Google has added yet another feature to Google Maps this week with the launch of the Transit Layer, which allows users to see public transport routes in 50 cities internationally.

Announced on Google's Lat Long Blog, the Transit Layer integrates Google Transit information directly with Google Maps for users to view and interact with.

The Transit Layer works slightly differently depending on which city the user views. In Perth, for example, users can see the layout of the entire public transit system, zoom in on a particular route and click on a bus stop to find out which bus routes pass through. Public transit users in Adelaide won't be able to see the network as a layer but can still click on bus stops and train stations, bringing up a window with colour-coded routes and a direct link to the Adelaide Metro Web site. Tram users in Adelaide can also see timetables.

Yesterday Google Maps was also displaying some public transport information for Melbourne, but a Google spokesperson told PC World that this was an "inadvertent mistake" and that the company has no plans to announce a similar service for Melbourne; the layer has since been disabled for the city.

Users have previously been able to obtain public transit directions in select cities when using Google Maps. The feature has been available in Perth since March and Adelaide since December. The directions feature can also be used in supported cities through Google Maps on iPhones with 2.2 firmware.