In recent years, Vehicle Ad Hoc Networks (VANETs) have become very popular. A VANET network is mainly constructed with an infrastructure composed of mobile vehicles and fixed Road Site Units (RSUs). RSUs are usually very expensive to install, this limits their number, especially in suburbs and areas of sparse population. Therefore, RSUs are precious resource in VANET. In order to promote the utility of RSUs, we propose a novel mechanism, Distributed Sorting Mechanism (DSM), to improve the efficiency of communication between vehicles and RSUs (Vehicle to Infrastructure, V2I). In DSM, every vehicle can individually calculate its own priority of communication, and the time to compete and obtain the channel can be reduced. We further consider the vehicles moving away from the coverage of communication and adjust their priorities of communication appropriately. Moreover, DSM owns the characteristic of “Deadline First” in specific situations. Using DSM not only simplifies the handoff procedure and reduces the network overhead, but also achieves adequate utilization of RSU resources.