As the rapid progress in vehicular communication technology, academic and industry pay more and more attention to vehicular ad hoc networks (VANETs). In VANETs, the dissemination delay and reliability are important criteria for many applications, especially emergency message dissemination. Existing approaches are hard to satisfy both requirements simultaneously due to the conflict between dissemination delay and reliability. In this paper, we propose a novel mechanism, named Fast and Reliable Emergency message Dissemination Mechanism (FR-EDM) to disseminate emergency message in VANETs. FR-EDM resolves the broadcast storm problem, achieves low dissemination delay, and provides the high reliability in freeway scenario. FR-EDM deliveries the emergency messages as soon as possible to the specific area (e.g., the area before the gateway) and guarantees all relevant vehicles receive the emergency messages in this area such that people can change their routes to destination in time. Consequently, people can avoid getting into a traffic jam. We use ns-2 simulations to evaluate our mathematical model for optimal block size and compare FR-EDM with other protocols. The simulation results show that FR-EDM achieves both lower dissemination delay and higher reliability than existing approaches.