I discuss a method we proposed to bound the Failures In Time (FIT) rate of a CAN-based real-time system, i.e., the expected number of failures in one billion operating hours. The method is based on an analysis of the probability of a correct and timely message transmission despite host and network failures due to electromagnetic interference (EMI), which we derived earlier. For a given workload, the derived FIT rate can be used to find an optimal replication factor, which is demonstrated with a case study based on a message set taken from a simple mobile robot.