In a vehicular ad hoc network (VANET), high mobility and uneven distribution of vehicles are important factors affecting the performance of routing protocols. The high mobility may cause frequent changes ofnetwork topology, while the uneven distribution of vehicles may lead to routing failures due to networkpartition, and even high density of vehicles may cause severe wireless channel contentions in an urban environment. In this paper, we propose a novel concept called the micro topology (MT), which consists of vehicles and wireless links among vehicles along a street as a basic component of routing paths and even the entire network topology.

We abstract the MT model reflecting the dynamic routing-related characteristics in practical urban scenarios along streets, including the effect of mobility of vehicles, signal fading, wireless channel contention and existing data traffic. We first analyze the endside-to-endside routing performance in an MT as a basis of routing decision. Then we propose a novel Street-centric Routing Protocol based on Micro Topology (SRPMT) along the streets for VANETs. Simulation results show that our proposed SRPMT protocol achieves higher data delivery rate and shorter average end-to-end delay compared with the performance of the GPSR and GyTAR.