Relative location information helps build vehicle topology maps. Such maps provide location information of nearby vehicles to drivers. In building a vehicle topology, one must consider various attacks on vehicular networks. Also the localization system should protect the drivers' identity and make it difficult for the adversary to track vehicles. Many techniques have been proposed for relative positioning and location verification. Due to the high speed and the strict security requirements, the existing relative positioning and location verification techniques are not directly applicable to vehicular networks. Hence, we present a scheme called Privacy-preserving Secure Relative Location Determination (P-SRLD), which securely determines the relative locations of a set of wirelessly connected vehicles based on the relative locations of each vehicle's surrounding vehicles. P-SRLD uses cryptographic keys to authenticate location messages and vehicle's cryptographic pseudonym to identify the vehicle to protect vehicle's driver's privacy. To defend against Sybil attacks, P-SRLD employs registration and relative location message verification mechanisms. It defends wormhole and blackhole attacks by probabilistically monitoring losses of relative location messages. Analysis and simulation results show that P-SRLD is lightweight and is resilient to Sybil, wormhole and some other attacks. Copyright © 2008 John Wiley & Sons, Ltd.