Risk homeostasis: Reducing risk does not necessarily reduce accidents

by Kathy Lubitz, President of the Ultralight Pilots Association of Canada and co-lead of the General Aviation Safety Campaign (GASC) Ultralight Working Group, as printed in the March 2016 issue of the Ultralight Pilots Association of Canada’s (UPAC) Light Flight)

This is the third article proposed by the Ultralight Working Group. This working group committed to writing an article for each edition of the Aviation Safety Letter (ASL) to promote safety best practices and culture, not only within the ultralight community, but also within the whole General Aviation community and in an even broader scope, as you will appreciate when reading this article. If you want to learn more or want to be part of a GASC Working Group, contact us at TC.GeneralAviation-AviationGenerale.TC@tc.gc.ca.

Risk homeostasis is the theory that every person has an acceptable level of risk that they find tolerable. It was proposed in 1982 by Dr. Gerald Wilde, a professor of psychology at Queen’s University, Ont.

Risk homeostasis theory states that, for any activity, people accept a particular level of subjectively evaluated risk to their health and safety in order to gain from a range of benefits associated with that activity. Wilde refers to this level of accepted risk as “target level of risk.”

Wilde uses a thermostat as an example of the target level of risk. A thermostat controls the actions of the heating/cooling unit which controls the temperature. This in turn controls the actions of the thermostat. There will be fluctuations in the room temperature, but averaged over time, the temperature will remain stable, unless the thermostat is set to a new target (set point) level.

Similarly, the target level of risk is seen as the controlling variable in the cause of the injury rate. The basic strategy of injury prevention should be to reduce the level of risk that people are willing to accept. Variations in skill or environmental conditions can only produce minor and/or short term fluctuations in target risk, not the set target risk.

If people subjectively perceive the level of risk as relatively low, they may modify their behaviour to increase their exposure to risk. Conversely, if they perceive a higher level of risk, they may exercise greater caution.

Risk homeostasis theory is counter-intuitive to the traditional approach to health and safety, in which it is believed that when initiatives don’t work as planned, we just need more or better controls or greater vigilance. Risk homeostasis explains why people don’t always respond as expected to traditional safety initiatives. Instead, they respond to these initiatives according to their own target level of risk.

In the risk and safety industry, it is common to try to isolate, focus on, and solve a particular problem or risk with a specific program or initiative. When the concept of risk homeostasis theory is not considered in the development and implementation of such efforts, those initiatives may not work out as planned or expected because of the subjective perceptions of risk, unconscious decisions, and biases and by-products associated with risk homeostasis.

Risk homeostasis proposes that rather than more controls, sometimes fewer controls and more motivation might be more effective. When the subjective perception of risk is greater and people make personal decisions about reducing it to an acceptable level (target risk), they will behave and adapt accordingly.

The above information is taken mainly from two articles. One is “Risk Homeostasis Theory: an Overview” by Gerald Wilde. The second is “Risk Homeostasis Theory–Why Safety Initiatives Go Wrong” by Dave Collins. Both sources offer the entire articles as well as references and suggested reading.

Drivers feel safer with cars that have ABS brakes and four-wheel drive, so they speed up. Smokers feel that “light” cigarettes are better for their health, so they smoke more of them. The requirement that made motorcycle drivers in Ohio wear helmets did not lower the death rate; the rule resulted in drivers feeling safer and an increase in speed and the number of fatalities. In each case, the risk was reduced in one area, so more was accepted in another.

Risk homeostasis and flying

How does risk homeostasis relate to flying? We accept the risk of defying gravity to take to the skies. We each have our own reasons to fly, just as we each have our own acceptable level of risk.

Relying on in-cockpit technology is an example of pilots accepting a higher level of risk. Before these technological advances were available, a pilot needed careful pre-flight planning along with maps and weather briefings.

Since all of this information is now at a pilot’s fingertips inside the cockpit, many just go without planning, relying on the equipment to let them know if they are going to run into a problem. They feel that the risk of the technology failing is low.

Consider the following example. A pilot uses two electronic aids to get to his or her destination: a global positioning system (GPS) with the aircraft’s position on a VFR Navigation Chart (VNC) and weather radar. The GPS tells the pilot where and how high he or she is. The weather radar shows the location of the rain/snow showers the pilot needs to avoid. Because of the low ceiling, the pilot makes the short flight at roughly 200 feet (ft) above ground level (AGL). The pilot is very familiar with the area, knows about the obstructions to avoid, and also has lots of flying experience and a way out if conditions become too bad to continue. The pilot makes it safely to the destination, admitting, however, that he or she probably should not have made the trip. It worked out, but in hindsight, it was risky… Maybe too risky. A word of caution: “getting away with it” also leads to accepting more risk next time. 

Another example: a pilot with a glass cockpit flies into deteriorating weather because the screen shows that once the aircraft makes it through the bad weather ahead, conditions will improve. The risk is that in-cockpit weather reports lag behind the actual weather by a few minutes (min) or up to to 20 min or more. Plus, a pilot also needs to know the conditions at the destination at the actual time of arrival an hour later. 

In both examples, the pilots relied on technology to get them safely to their destination. They risked the failure of the technology. Batteries might die and the pilot would have to change them mid-flight and re-start, hopefully with the program intact. A GPS might lose its signal and not keep track of its current location. Weather conditions are not in real time and may not accurately reflect the current situation.

There can be software problems. Owners of some older Dynons actually had this happen when a software update initially caused the screens to freeze up during flight.  This is reportedly now fixed, and newer models should not have this problem. 

Accident statistics show that flight into instrument conditions by pilots who are not able to handle the situation causes many serious accidents. The risk tolerance of these pilots does not match their abilities. Five hours of practice “under the hood” for the Private Pilot Licence may give a pilot confidence to continue into deteriorating weather because he or she has had the training to escape from trouble should he or she encounter instrument conditions.

Another example involves a pilot making an approach on a marginal runway. The pilot asks, “Can I make it?” Yes? No? Yes? No? The pilot can’t decide. Indecision is the decision; the answer is no. When the outcome is in question, and the risk is right on the edge of what’s acceptable, the decision should be it’s too risky.

If you get nothing else from this article, please at least be aware of risk homeostasis and your personal target risk. Recognize it when you find yourself trying to justifying a proposed action or when you have the potentially dangerous attitude that “I’m safe enough”.

We must accept that flying is risky. When we defy gravity, things can go wrong and we can get hurt, or worse. The rewards for accepting the risk can be great, but be realistic about your abilities. Keep yourself safe so that every flight has a happy ending.