Vehicle collisions at intersections account for a large percentage of overall traffic accidents, a good portion of which are fatal. A large number of these accidents can be avoided by a warning system which makes a driver aware of potential collisions on the road, thus allowing the driver enough time to prevent such situations. This paper presents the design of a prototype intersection collision warning system based on vehicle infrastructure integration (VII). Moreover, we design a system consisting of roadside and on-board units, in which appropriate alarm messages are disseminated by the roadside unit in case it predicts a potential collision at the intersection to notify endangered vehicles of the moving car which is about to cross the red light. Furthermore, we implemented the proposed configuration in a real world scenario whose promising results in the form of negligible probability of false alarm, renders the system a fine benchmark for future more detailed and realistic studies. Underlying the system are wireless communications, positioning technology, and information technology that ensure accurate and timely safety information.