Web technologies provide simple and efficient means to develop and maintain applications for a large number of clients. This advantage should also be leveraged for the purpose of intelligent transportation system (ITS) applications on vehicle onboard systems. However, Web applications have some disadvantages in a vehicular environment like a restricted browser execution environment, no or limited access to local vehicle data/functions and the need for a continuous mobile network connection. Web 2.0 technologies are able to cope with these drawbacks. This paper presents the result of a study on how novel Web technologies enable real-time ITS applications for vehicle on-board systems. An assessment of Web tools and technologies for this application domain is given as well as the proof-of-concept by an exemplary ITS Web application. The prototype application enables real-time road traffic warning distribution across vehicles.