Safety can be limited in relation to some guarantee or a standard of insurance to the quality and unharmful function of an object or organization. It is used in order to ensure that the object or organization will do only what it is meant to do.
It is important to realize that safety is relative. Eliminating all risk, if even possible, would be extremely difficult and very expensive. A safe situation is one where risks of injury or property damage are low and manageable.
When something is called safe, this usually means that it is safe within certain reasonable limits and parameters. For example, a medication may be safe, for most people, under most circumstances, if taken in a certain amount.
A choice motivated by safety may have other, unsafe consequences. For example, frail elderly people are sometimes moved out of their homes and into hospitals or skilled nursing homes with the claim that this will improve the person’s safety. The safety provided is that daily medications will be supervised, the person will not need to engage in some potentially risky activities such as climbing stairs or cooking, and if the person falls down, someone there will be able to help the person get back up. However, the end result might be decidedly unsafe, including the dangers of transfer trauma, hospital delirium, elder abuse, hospital-acquired infections, depression, anxiety, and even a desire to die.
Types
There is a distinction between products that meet standards, that are safe, and that merely feel safe. The highway safety community uses these terms:
Normative
Normative safety is achieved when a product or design meets applicable standards and practices for design and construction or manufacture, regardless of the product’s actual safety history.
Substantive
Substantive or objective safety occurs when the real-world safety history is favorable, whether or not standards are met.
Perceived
Perceived or subjective safety refers to the users’ level of comfort and perception of risk, without consideration of standards or safety history. For example, traffic signals are perceived as safe, yet under some circumstances, they can increase traffic crashes at an intersection. Traffic roundabouts have a generally favorable safety record yet often make drivers nervous.
Low perceived safety can have costs. For example, after the 9/11 attacks in 2001, many people chose to drive rather than fly, despite the fact that, even counting terrorist attacks, flying is safer than driving. Perceived risk discourages people from walking and bicycling for transportation, enjoyment or exercise, even though the health benefits outweigh the risk of injury.
Security
Also called social safety or public safety, security addresses the risk of harm due to intentional criminal acts such as assault, burglary or vandalism.
Because of the moral issues involved, security is of higher importance to many people than substantive safety. For example, a death due to murder is considered worse than a death in a car crash, even though in many countries, traffic deaths are more common than homicides.
Risks and responses
Safety is generally interpreted as implying a real and significant impact on risk of death, injury or damage to property. In response to perceived risks many interventions may be proposed with engineering responses and regulation being two of the most common.
Probably the most common individual response to perceived safety issues is insurance, which compensates for or provides restitution in the case of damage or loss.
System safety and reliability engineering
System safety and reliability engineering is an engineering discipline. Continuous changes in technology, environmental regulation and public safety concerns make the analysis of complex safety-critical systems more and more demanding.
A common fallacy, for example among electrical engineers regarding structure power systems, is that safety issues can be readily deduced. In fact, safety issues have been discovered one by one, over more than a century in the case mentioned, in the work of many thousands of practitioners, and cannot be deduced by a single individual over a few decades. A knowledge of the literature, the standards and custom in a field is a critical part of safety engineering. A combination of theory and track record of practices is involved, and track record indicates some of the areas of theory that are relevant. (In the US, persons with a state license in Professional Engineering in Electrical Engineering are expected to be competent in this regard, the foregoing notwithstanding, but most electrical engineers have no need of the license for their work.)
Safety is often seen as one of a group of related disciplines: quality, reliability, availability, maintainability and safety. (Availability is sometimes not mentioned, on the principle that it is a simple function of reliability and maintainability.) These issues tend to determine the value of any work, and deficits in any of these areas are considered to result in a cost, beyond the cost of addressing the area in the first place; good management is then expected to minimize total cost.