Vehicular Ad hoc Network (VANET) is new network type which is used for short range high speed communication among vehicles and between vehicles and road side infrastructure units. In most of the existing literature, the gateways are considered static, deployed on the road side at fixed distance from each other, depending on their transmission range, which makes the overall system costly. The proposed work is for enabling the mobile data access for vehicle anytime and anywhere. Dynamic clustering of vehicles is used to achieve this access of mobile data in vehicles. Clustering is done here based on zone based approach and by considering the dwelling time of vehicles with their velocity. Dwelling time of a vehicle is the time of that vehicle that resides in a particular range. Zone based clustering is similar to normal clustering but all of the members of this clusters can act as cluster head. The different clusters can be overlapping each other. The velocity of vehicles taken here are 40m/s, 60m/s, 80m/s and 100m/s. The velocities of vehicles in same track have same velocities for simplifying the simulation. Requirements of vehicles such as ambulance, fire service vans are crucial during emergency situations. Hence such vehicles need to be given a high priority in this network architecture. Prioritization of vehicles can be done by considering inter vehicular communication property calculating the deviation of vehicular velocities.