Road traffic congestion in urban areas and metropolitan cities is becoming nowadays an increasingly critical issue. With the advances in wireless technologies and the emergence of vehicle to vehicle communication techniques, new research studies are carried out to develop new applications and services over vehicular ad hoc networks for road safety and road traffic management. In this paper we present a peer-to-peer VANET application for sharing and exchanging road traffic information which allows vehicles to detect and avoid road congestion. We designed a pull-based geocast protocol which allows vehicles to cooperatively collect and disseminate data in an efficient way. This protocol is integrated with a caching mechanism which reduces the amount of information exchanged between vehicles. We show that despite the use of caching, we managed to preserve the accuracy of the traffic information collected and obtain equivalent results for the overall road traffic congestion reduction.