Safety-critical real-time systems are being designed using off-the-shelf components connected together to provide the different functions expected from the system. In such architectures, the communication backbone plays an important role in helping systems meet their timing constraints. Components are typically connected via buses, and often components are connected to more than one bus. We describe an approach to synthesizing routes such that all messages meet their deadlines in distributed systems built using bus-based networks when the traffic characteristics are known in advance. This work is the starting point for further work which will allow network resources to be allocated dynamically when traffic patterns cannot be determined at design-time.