Traffic congestion has been an inevitable problem in urban areas. The traffic congestion not only causes economic loss and environment pollution, but also hurts peoples' health. Intelligent Transportation System (ITS) is developed to improve traffic management and among others. To amend existing traffic congestion control mechanism, in this research, we proposed a virtual data sink based information dissemination mechanism in vehicular ad hoc networks. A concept of virtual TTI (Traffic and Travel Information) sink is introduced to collect information of traffic volume and disseminated via cooperative inter-vehicle communications. With the help of our mechanism, the traffic congestion situation is predicted and travelling time is estimated. We took into account factors including traffic and travel information, road scale and topology in our mechanism. Our proposal is examined by extensive simulation. The simulation results show that average travelling time is significantly reduced with little network bandwidth consumption. The problem of overwhelming broadcast message is also effectively controlled.