FlexRay is an automotive network communications protocol developed by the FlexRay Consortium to govern on-board automotive communications.
It is designed to be faster and more reliable than CAN, but it is more expensive.
The FlexRay consortium disbanded in 2009, but the FlexRay standard is now a set of ISO standards, ISO 17458-1 to 17458-5.
FlexRay supports data rates up to 10 Mbit/s, explicitly supports both star and bus topologies, and can have two independent data channels for fault-tolerance (communication can continue with reduced bandwidth if one channel is inoperative).
The bus operates on a time cycle, divided into two parts: the static segment and the dynamic segment. The static segment is pre-allocated into slices for individual communication types, providing stronger determinism than its predecessor CAN. The dynamic segment operates more like CAN, with nodes taking control of the bus as available, allowing event-triggered behaviour.
FlexRay has certain disadvantages like lower operating voltage levels and asymmetry of the edges, which leads to problems in extending the network length and this is why it is often used in a star topology with a hub / switch ECU isolating the limbs of the star.
Ultimately Ethernet (Broadr Reach) will replace FlexRay for bandwidth intensive, non-safety critical applications.