This paper presents a novel approach to increase the safety of road travel using the concept of wireless sensor networks for intelligent transportation systems (ITS). Safety of road travel can be increased if vehicles can be made to form groups for mutual interaction with each other. With the number of sensors available on vehicles increasing, a need has arisen to make collaborative use of the information collected by individual vehicles to form an enhanced data set to improve the inter-vehicle

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... safety features. We discuss how a group of vehicles can form a mobile ad hoc sensor network and exchange data sensed by the on-board sensors. The fusion of these data could give a better understanding of the surrounding traffic conditions. An inter-vehicle communication (IVC) protocol which decides the manner of data exchange among vehicles based on the data contained in the messages is utilized for communication among vehicles. These messages are divided into two main types, namely, periodic and alert messages. Periodic messages can be generated by a sensor based control system on the vehicle and are transmitted at regular intervals to inform other vehicles. Alert messages are generated by the vehicle in an emergency situation, like, after an air-bag deployment. This differentiation is needed since periodic and alert messages are used to convey different types of data under different situations. This work also discusses exchange of alert messages between vehicles and fixed roadside gateways. This type of vehicle to vehicle and vehicle infrastructure integration (VII) raises the safety of road travel. Results of simulations in network simulator (ns-2), MATLAB and hardware experiments with mobile sensor nodes prove the effectiveness of the proposed IVC protocol for providing safety-related services to vehicles.