VEHICLE SAFETYASIL

VEHICLE SAFETY(ASIL) Automotive Safety Integrity Level(ASIL) is of classifying hazards, risk,

quality, or reliability scheme defined by the ISO 26262 - Functional Safety for Road Vehicles standard.

  The ASIL is established by performing a risk analysis of a potential hazard by looking at the Severity, Exposure and Controllability of the vehicle operating scenario.There are four ASILs identified by the standard: ASIL A, ASIL B, ASIL C, ASIL D. ASIL D dictates the highest integrity requirements on the product and ASIL A the lowest. In the context of ISO 26262, a hazard is assessed in terms of severity of possible injuries within the context how much of the time a vehicle is exposed to the possibility of the hazard happening as well as the relative likelihood that a typical driver can act to prevent the injury.In short, ASIL refers both to risk and to risk-dependent requirements Whereas risk may be generally expressed as:Risk=(expected loss in case of the accident) x (probability of the accident occurring) and ASIL may be expressed as:ASIL= Severity X Exposure X Controllability

The severity (S) of injuries can be classified as:S0 No InjuriesS1 Light to moderate injuriesS2 Severe to life-threatening (survival probable) injuriesS3 Life-threatening (survival uncertain) to fatal injuriesExposure (E) (the relative expected frequency of the operational

conditions in which the injury can possibly happen) and classified as:E0 Incredibly unlikelyE1 Very low probability (injury could happen only in rare operating conditions)E2 Low probabilityE3 Medium probabilityE4 High probability (injury could happen under most operating conditions)Controllability Classifications (C):C0 Controllable in generalC1 Simply controllableC2 Normally controllable (most drivers could act to prevent injury)C3 Difficult to control or uncontrollable

So, ASIL D is the highest level of hazard and can be computed as:ASIL D= S3*E4*C3

For each single reduction in any one classification from its maximum value (excluding reduction of C1 to C0), there is a single level reduction in the ASIL from D. [For example, a hypothetical uncontrollable (C3) fatal injury (S3) hazard could be classified as ASIL A if the hazard has a very low probability (E1).] The ASIL level  A is the lowest level,