In this paper we describe the application of wireless sensor networking techniques to address the realization of a safe and secure decentralized traffic management system. We consider systems of many heterogeneous autonomous vehicles moving in a shared environment. Each vehicle is assumed to have different and possibly unspecified tasks, but they cooperate to avoid collisions. We are interested in designing a scalable architecture capable of accommodating a very large and dynamically changing number of vehicles, guaranteeing their safety (i.e., collision avoidance), the achievement of their goals, and security against potential adversaries. By properly distributing and revoking cryptographic keys we are able to protect communications from an external adversary as well as to detect non-cooperative, possibly malicious vehicles and trigger suitable countermeasures. In our architecture, scalability is obtained by decentralization, i.e. each vehicle is regarded as an autonomous agent capable of processing information concerning its own state and the state of only a fixed, small number of ``neighboring'' agents. Ad-hoc wireless sensor networks are employed to provide support for this architecture.