Google has built up an extensive amount of mapping and layered data. They have even devised a multiple transit data feeds to allow one to obtain information (GTFS). This feed data on transit should really be available in every city of the world to help commuters travel around with ease of accessibility of information. London specifically also has a Transport for London feeds service on a whole range of information available. Unfortunately, as there is no real agreed global standard it creates for added complexities of data aggregation on transit within the various cities of the world who each seem to have their own approaches. Majority of the mapping work on Google Maps is done in JavaScript. But, there are also alternatives available like Leaflet.js, OpenLayers, Yahoo Maps and more. Unfortunately, one major drawback of relying on Google APIs or for that matter any commercial vendor specific APIs for data is that they provide no reliability for long term availability of the service or that it might in fact change over time on which one might have in fact built a web application. It would be useful on some providers to support versions of their APIs that way backward compatibility can save many who rely on their services. Also, travel information can potentially also be semantically applied using linked data from geonames.
