Ensuring fast and reliable dissemination of safety messages is a prerequisite for the establishment of safety applications in Vehicular Ad Hoc Networks (VANETs). However, fulfilling this requirement is a challenging task due to the specific characteristics of VANETs and the increasing density of vehicles in urban areas. Moreover, VANETs may carry a large amount of data to moving vehicles, leading to an excessive load on the network, which might significantly decrease the performance of the applications. The existing solutions address this problem by either reducing the beacons transmission rate or controlling the vehicles' transmission power. We argue that such a network could control its load and improve the transmission reliability by improving the forwarding mechanism. To this end, we propose the Road-Casting Protocol, a distributed dissemination protocol for safety messages in urban areas, which is based on a cooperative forwarding mechanism that reduces the number of unnecessary retransmissions and shortens the end-to-end delay. We have evaluated the efficiency of our protocol using realistic simulations, based on an accurate propagation loss model for urban communications in VANETs, and the obtained results are very promising.