Vehicle bus systems are primarily used for communication between control units. They make it possible to share information once it has been generated, for example variables recorded by sensors. This greatly reduces the number of sensors, but also the required cable lengths.
This approach has an enormous impact on the development cycle: on the one hand, the bus information can be reused. For example, no dedicated measurement hardware needs to be installed in test systems if an ECU already performs this task. On the other hand, many ECU functions require information from other ECUs, which then often has to be simulated.
In addition, simulation is always helpful when a vehicle or ECU is needed but is not available. This is the case in test preparation to verify test cases or the test setup, but also in regression testing. And in training facilities, a simulation also facilitates the work enormously because the test object is always available.