Acceptable Level of Safety Performance (ALoSP)

Acceptable Level of Safety Performance (ALoSP)


The level of safety performance agreed by State authorities to be achieved for the civil aviation system in a State, as defined in its State safety programme, expressed in terms of safety performance targets and safety performance indicators. (ICAO Doc 9859: Safety Management Manual, Fourth Edition, 2018)


The acceptable level of safety performance (ALoSP) to be achieved is to be established by the State.

Absolute safety is generally an unachievable and very expensive goal. Overallocation of resources to safety may result in any change being unfeasible. On the other hand, neglecting the safety aspect may lead to an accident. Therefore the concept of safety space has been adopted in aviation. The term "safety space" is a metaphor for the zone where an organization balances desired production/profitability while maintaining required safety protection through safety risk controls.  This approach is also applicable to the State’s management of its State safety programme (SSP), given the requirement to balance resources required for State protective functions that include certification and surveillance.

For the purpose of an SSP, the ALoSP is identified and established by the State’s aggregate safety indicators. State safety indicators used for this purpose are those which have objective targets and alert settings incorporated. Therefore, ALoSP is the overarching concept while safety indicators with their corresponding alert and target levels are the actual metrics.

The result of the safety management processes is "to facilitate achievement of an acceptable level of safety while balancing the allocation of resources between production and protection.". (ICAO Doc 9859)

Traditionally, in many industries including aviation, safety regulation has been carried out prescriptively, i.e. the regulator defines the rules and standards to be followed and uses audit and inspection to check compliance with them. This approach requires a great deal of specialist resource on the part of the regulator and is often over-constraining for the regulated entity, particularly in the introduction of new processes and technologies.

The ALoSP concept complements this traditional approach to safety oversight with a performance-based approach that defines actual safety performance levels within a prescribed SSP framework. Safety is much more clearly the responsibility of the operator/service provider, the regulator’s role being mainly to ensure that the service provider discharges his responsibilities properly. The regulator sets objectives for the achievement and demonstration of safety - acceptable (or tolerable) safety levels - and the service provider has to show (by argument and evidence) that those objectives have been met.

ALoSP is expressed by two specific metrics, namely safety performance targets and safety performance indicators. Safety indicators are tactical monitoring and measurement tools while targets define long-term SSP safety performance objectives. A fully developed ALoSP monitoring and measurement process will:

  • identify all the safety-critical sectors and the safety indicators that define the level of safety in these areas;
  • identify targets that define the level to be maintained or desired improvement to be achieved for relevant indicators in each sector;
  • identify alerts that will indicate an actual or developing safety performance problem in a particular safety indicator or sector;
  • review SSP safety performance to determine whether modifications or additions to existing indicators, targets or alerts are needed to achieve continuous improvement.

A State’s basic safety indicators generally consist of high-consequence safety indicators (e.g. accident and serious incident rates). Such data is normally expressed in terms of rate instead of absolute numbers. Subsequently (at a mature ALoSP stage), lower-consequence safety indicators may be developed.

Once a State’s ALoSP package has been defined, it is possible to compile a summary of the performance outcomes of each safety indicator on a regular basis. The target and alert level for each indicator may then be checked for their respective performance (achievement) status. A consolidated summary of the overall performance outcome may then be compiled for a particular period.

To ensure that the ALoSP safety indicators remain effective and appropriate over time, they need to be reviewed periodically and updated as necessary.

Note: The establishment of ALoSP safety indicators, targets and alerts does not replace or supersede the need for States to implement all applicable SARPs.

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