This paper addresses the formal specification and verification of situated multi-agent systems that can be formulated within the influence-reaction model as proposed in 1996 by Ferber & Muller. In this framework our objective is to prove the correctness of reactive multi-agent systems with respect to a certain formal specification or property, using formal methods. This is an important step to bring multi-agent systems to high quality standards as required for critical applications encountered in domains such as transport systems. A generic B writing of systems instantiating the influence reaction model is proposed, using patterns of specification. An illustration is then presented on the formal specification of a system operating electrical vehicles under precise automatic control at close spacings to form a platoon. The papers ends with considerations about further improvements of the framework, involving simulation and study of the properties of the system.