Objective safety can be described as the actual number or risk of accidents or injuries, while subjective safety is the feeling or perception of safety, i.e. how people subjectively experience accident risk.

Subjective

An example from a well-known risk textbook is an icy sidewalk. A child might see that as a fun thing to slide on so their perception is that there is no risk. A retiree will perceive this as a high risk as their chance of falling and becoming injured is higher and more debilitating. If a kid falls, they usually just get up and carry on with what they are doing.

Here, the perception of the same situation is very subjective.
Secondly, how a similar situation affect an individual or group depends on their particular circumstances.

Risk as a combination of a threat, vulnerability to that threat and the impact of that threat. So risk = threat * vulnerability * impact. 

This is a less-rigid use of ‘subjective’ but the point is that the risk posed by a similar situation is still influenced heavily by personal factors.

Subjective probability is a person’s perception of the likelihood of an event. Subjective probability differs from objective probability, either because the person cannot calculate the actual probability or because the person feels lucky or unlucky.

Objective

Objectivity is therefore hard to achieve because of this subjectivity and because many of the biases and influences we experience are subconscious and linked to System 1 (instinctive, fast) thinking. However, it is because of these biases that we need objective measures to help us begin risk discussions from a relatively neutral point.

Data is a big help here (assuming we have eliminated as much bias from the data collection as possible).

So if we can gather enough data to give us a good understanding of what the threat looks like (say, the frequency and magnitude of earthquakes in a particular area), we can then start to assess the vulnerability and impact and therefore the risk of this kind of event more objectively.

So if we can gather enough data to give us a good understanding of what the threat looks like (say, the frequency and magnitude of earthquakes in a particular area), we can then start to assess the vulnerability and impact and therefore the risk of this kind of event more objectively.

In this example, anyone who has experienced an earthquake will have a different (subjective) perception of the risk from someone who hasn’t but at least they could begin their discussion from a neutral (objective) position using a data-driven threat assessment. 

Objective probability is the probability of an occurrence, calculated by either deduction or induction. A priori probability is a probability deduced by determining the ratio of a given outcome to finite possibilities of equal probability.

The Degree of Risk Depends on Both Magnitude and Probability

The degree of risk depends not only on the probability of loss, but also on the magnitude of the loss. Hence, if 2 loss events have the same probability of occurrence, but one of the losses exceeds the other, then the greater potential loss is the greater risk. So, if there was an equal probability of losing $1 or $100, then the risk of losing $100 greater than the risk of losing $1. Because insurance companies compensate for losses by paying money to the insured, it must calculate both the magnitude and probability of potential losses to set a premium that will cover those losses and earn the insurance company a profit.Thus, the main risk for an insurance company is that actual losses will exceed expected losses.

Andrew Sheves

mindFly

Take the example of the Khozikode airport which has been in the news of late. The runway dimensions, the Runway End Safety Area (RESA), the Runway Strip, Runway Lighting etc. may be compliant with ICAO Annex-14 requirements but also be viewed from a Safety Risk point of view too.

The same runway located on a flat floor with enough open space around will be a safe runway to operate from. However, the moment the same runway is located on top of a hill, in this case a table top runway, the magnitude of risk increases several times. Even though both runways have similar dimensions and both comply with ICAO Annex-14 requirements, they subjectivity of risk is different when a risk assessment is carried out for both the runways.

Therefore, a runway on a table top needs to have greater safety buffers. The runway must be equipped with approach lights, threshold lights, centerline light, engineered material arresting system, wider runway strip etc. This is to improve pilot awareness, decision making and error management. This is a buffer over and above the minimum requirements, catered for the higher degree of risk