 International standard IEC 61511 was published in 2003 to provide guidance to end-users on the application of Safety Instrumented Systems in the process industries.This standard is based on IEC 61508, a generic standard for functional safety including aspects on design, construction, and operation of electrical/electronic/programmable electronic systems.Other industry sectors may also have standards that are based on IEC 61508, such as IEC 62061 (machinery systems), IEC 62425 (for railway signaling systems), IEC 61513 (for nuclear systems), and ISO 26262 (for road vehicles, currently a draft international standard).