OSEK is a an industry standard rtos that is used by almost all automotive players. It is specifically designed for use in the automotive environment. Toyota actually claimed to use an OSEK compliant rtos, but it later surfaced in this lawsuit that they had written their own implementation that was never certified by an outside organization. OSEK is in the process of being superseded by AUTOSAR, which defines much more than just the os, and included a large hal that allows for plug and play middleware libraries. Unfortunately it isn't economical for every ecu to make use of AUTOSAR: it has heavy resource requirements (> 2Mbyte RAM) and so many applications don't use it.

Also on the horizon is ISO26262, which mandates quality assurance for automotive embedded code in the form of paper trails. Unfortunately due to the huge amount of work required by the standard, some automakers are choosing to ignore it and hope it doesn't become mandatory.