Safety performance acceptable risk” defined

Arrester Testing and Standards Regulatory and approval agencies and insurers impose acceptance testing requirements, sometimes as part of certification standards. The user may also request testing to demonstrate specific performance needs, just as the manufacturer can help develop standards. These interrelationships have resulted in several new and updated performance test procedures. Listing of an arrester by a testing laboratoiy refers only to performance under a defined set of test conditions. The flame arrester user should develop specific application requirements based on the service involved and the safety and risk criteria adopted. 

There are of course many mathematically complex ways to perform a risk assessment, but first key questions about the biological data must be resolved. The most sensitive endpoint must be defined along with relevant toxicity and dose-response data. A standard risk assessment approach that is often used is the so-called divide by 10 rule . Dividing the dose by 10 applies a safety factor to ensure that even the most sensitive individuals are protected. Animal studies are typically used to establish a dose-response curve and the most sensitive endpoint. From the dose-response curve a NOAEL dose or no observed adverse effect level is derived. This is the dose at which there appears to be no adverse effects in the animal studies at a particular endpoint, which could be cancer, liver damage, or a neuro-behavioral effect. This dose is then divided by 10 if the animal data are in any way thought to be inadequate. For example, there may be a great deal of variability, or there were adverse effects at the lowest dose, or there were only tests of short-term exposure to the chemical. An additional factor of 10 is used when extrapolating from animals to humans. Last, a factor of 10 is used to account for variability in the human population or to account for sensitive individuals such as children or the elderly. The final number is the reference dose (RfD) or acceptable daily intake (ADI). This process is summarized below. 

Top-level criteria and requirements are defined primarily from two sources the regulator, whose concern is primarily public health and safety, and the user, whose concern is all encompassing (e.g. safety, performance, availability, and economics). Each of the four Goals has been quantified by a series of top-level criteria and requirements (Ref. 1, 2). The Top-Level Regulatory Criteria are a necessary and sufficient set of direct quantitative statements of acceptable health and safety consequences (doses) or risks to the public that are independent of reactor type and site. Demonstration of... 

The government agency (or other procuring organization) for whom a system (or product) is being developed must determine the objectives and specifications for the project. The specifications should include standards of safety performance and define the levels of acceptable risk. The specific system safety tasks and requirements must also be defined. 

Safety must be placed in its proper perspective. A correct safety balance cannot be achieved unless acceptable and unacceptable conditions are established early enough in the program to allow for the selection of the optimum design solution and/or operational alternatives. Defining acceptable and unacceptable risk is as important for cost-effective accident prevention as is defining cost and performance parameters [11]. 

A safety requirement is to keep a safe distance to the car ahead while being activated (see Rl). For each safety requirement the integrity or the reliability must be defined. For the CACC only integrity is required, because it is safe to switch off the functionality and inform the driver in case of a failure. The risk analysis performed in the first step showed that a probability of at most 10 untreated random errors per hour (that may lead to an accident) can be accepted. Hence, for Rl it can be stated that... 

Any review of NHTSA decisions about vehicle safety standards must recognize the assumption on which the safety mandate is based and the judgment required to interpret the directions given. The fundamental assumption is that there are too many traffic injuries and that regulatory action must be taken to reduce them to an acceptable level. The stated purpose of the Vehicle Safety Act is to reduce traffic accidents and death and injury from traffic accidents the assumption is that losses without the law are unacceptable. Motor vehicle safety is defined in the statute as vehicle performance which protects persons against unreasonable risks the assumption is that vehicle safety standards will reduce the risks to a reasonable level. Standards are supposed to be practicable in terms of several factors including the ultimate cost (if any) to the consumer. 

FMEA is used to assist analysts to perform hazard analyses and it is regarded as a supplement rather than a replacement for hazard analyses. Safety analysts can use FMEA to verify that all safety critical hardware has been addressed in the hazard analyses. The FMEA for hardware systems is an important technique for evaluating the design and documenting the review process. All credible failure modes and their resultant effects at the component and system levels are identified and documented. Items that meet defined criteria are identified as critical items and are placed on the Critical Item List (CEL). Each entry of the CIL is then evaluated to see if design changes can be implemented so that the item can be deleted from the CIL. Items that cannot be deleted from the CIL must be accepted by the programme/project, based on the rationale for acceptance of the risk. The analysis follows a well-deflned sequence of steps that encompass (1) failure mode, (2) failure effects, (3) causes, (4) detectability, (S) corrective or preventive actions, and (6) rationale for acceptance. 

The safety/risk criteria. The safety/risk criteria establish the top-level system safety requirements, or objectives. Regulatory authorities may have different definitions for the various categories of hazards/accidents. To be able objectively to distinguish and evaluate the various hazards present, it is important to define the exact terminology and to allocate a measure of performance. This is an important (and arguably most neglected) topic as it is the safety acceptance criteria the system is expected to achieve, and hence the measure (or standard) the assessment will compare the system against. For more detail on safety criteria, see Appendix B. The system level. Define the systems level at which safety is to be assessed. The importance of this step is explained in Section 8.3 above. A safety assessment by a supplier of a component (e.g. a flare dispenser) will vastly differ in scope and approach to a safety assessment for a product (e.g. an aircraft) or user system (e.g. a facility). 

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