Abstract. Embedded systems for safety-critical applications often integrate multiple “functions ” and must generally be fault-tolerant. These requirements lead to a need for mechanisms and services that provide protection against fault propagation and ease the construction of distributed fault-tolerant applications. A number of bus architectures have been developed to satisfy this need. This paper reviews the requirements on these architectures, the mechanisms employed, and the services provided. Four representative architectures (SAFEbus TM, SPIDER, TTA, and FlexRay) are briefly described. 1