The Truth About Airbags and Avalanche Survival


riding the storm out 660This winter I noticed a magazine advertisement for an avalanche airbag pack that claimed “a 97 percent success rate in real world conditions.” What the advertisement didn’t mention was that people caught without an avalanche airbag have an 80 to 90 percent success rate. In other words, most people caught in an avalanche will get a cheap lesson; they will either escape off the slab, grab a tree, dig into the bed surface, ride on top of the debris, be saved by a beacon recovery, or just plain get lucky. Most people caught in an avalanche will survive, which is very good news for all of us.

It reminds me of the example my college statistics professor presented in which Sanka advertised their decaf coffee as “97 percent caffeine free.” What they didn’t tell you was that regular coffee is 90 percent caffeine free. This, no doubt, sells much more coffee than saying that their decaf coffee has one-third the caffeine as regular coffee, which is much less misleading.

There seems to be no end of confusion about the effectiveness of avalanche airbags. I have heard survival numbers ranging from 97 percent to 3 percent. (“Avalanche airbags would save only 3 out of 100 who would have otherwise have died,” said a prominent avalanche professional in a national class.) That’s a wide range of disagreement.

Today, I want to explain why the numbers vary so dramatically and provide what I think is a more useful — and less misleading — sound bite when we talk about the effectiveness of avalanche airbags.

Most airbag data come from Europe because avalanche airbags were developed there and over the past 15 years they have become ubiquitous. There have been close to 400 documented cases of people getting caught with avalanche airbags (the exact amount is uncertain because many non-fatal cases likely go unreported).

The “97 percent success rate” comes from a database maintained by the Swiss Federal Institute of Snow and Avalanche Research (SLF). In collaboration with ABS brand of avalanche airbags, SLF kept track of all the people that reported being caught in an avalanche with an avalanche airbag, whether they successfully deployed it or not, until the fall of 2010. After that, the responsibility for collecting data was passed to national avalanche centers.

According to a 2007 study of this dataset, the percentage of people caught who died in an avalanche decreased from 19 percent to 3 percent for those who successfully deployed an avalanche airbag. In other words, there is an 81 percent “success rate” for those without a deployed airbag and a 97 percent “success rate” for those who did.

Thus, many people have latched onto the 97 percent figure. But we have to remember that this is 97 percent of those caught. Because most of people caught survive anyway, the number most of us are probably more interested in is what percentage would survive who would have otherwise been killed. (In statistics-speak, this is the difference between “absolute reduction in mortality” and “relative reduction in mortality.” Back to the Sanka coffee example, this is the difference between being “97 percent caffeine free” and “one-third the caffeine of regular coffee.”)

At the International Snow Science Workshop last fall, the well-respected Canadian researcher, Pascal Haegeli presented some preliminary results of his more up-to-date study on the effectiveness of avalanche airbag packs. He performed the study like standard medical research in which he compared the mortality rate of the treatment group with the control group (people who wore airbags vs. those who did not). As I mentioned before, there is a wide variety in the severity of the avalanche that can catch people. So he only included the cases where people were “seriously involved,” meaning that the avalanche airbag “had a chance to be effective.” In addition, he only included cases with multiple victims in which — in the same avalanche — some wore airbags and some did not, and he also included cases where people failed to deploy the airbag. In other words, he wanted to fairly compare the success of the technology, warts and all. He still needs to add more data from Europe and publish it in a peer-reviewed journal, so I can’t present the numbers here, but his preliminary results suggest the following:

If you look at it optimistically, a deployed airbag saved about half of those who would have otherwise died. If you look pessimistically, you would say that half of the people who deployed airbags died anyway.

Not all people who wore airbags were able to deploy them. If you include these cases, wearing an avalanche airbag saved about a third of those who would otherwise have died.

Pascal was careful to mention that his study presented perhaps a worst-case scenario because, he eliminated less serious avalanches from the analysis and included only multiple burial incidents, and thus the data was biased towards larger, less survivable avalanches.

Indeed, in the April 2012 issue of the Avalanche Review, Jonathan Shefftz did a great summary of five different published data sets, mostly from older European data, and he found roughly similar numbers. Wearing an avalanche airbag would have saved from 35 to 81 people out of 100 who would have otherwise died. (The average of the five studies is 64.) So, it seems that in real-world experience, wearing an avalanche airbag will possibly save a little more than half of those who would have otherwise died.

From my perspective, preventing half of avalanche fatalities is pretty darn good. Avalanche airbags are the best technology we have seen, including the beacon. Although it’s impossible to directly compare beacons with avalanche airbags because they do dramatically different things, most experts agree that the avalanche airbag will likely save more lives.

My pet peeve with this issue is that people who argue about the numbers often leave the most important part out of the discussion – terrain. If you are caught in un-survivable terrain, by definition you won’t survive no matter what kind of rescue gear you use. There have been a number of prominent accidents in which the victim with a deployed airbag died because he was either strained through thick trees and rocks, deposited in a terrain trap, buried deeply, or went over a cliff. In zero-tolerance terrain, airbags don’t work, beacons don’t work, Avalungs don’t work. Nothing works. Save your money, buy a life insurance policy, and use a RECCO so rescuers don’t have to spend all night probing.

So at least for me, unless I’m 99.9 percent certain that the slope won’t slide, I don’t go to un-survivable terrain. If I’m going to spend the money and carry the extra weight of an avalanche airbag pack, I want to ride in terrain where it has a chance to make a difference. In other words, you should choose terrain with no obstacles, no terrain traps or sharp transitions, and avoid large avalanche paths.

The other part of the situation is the often-overlooked issue of what we call “risk homeostasis.” Each gizmo we acquire to increase our safety usually causes us to increase our level of risk at the same time. For instance, when we added seat belts and airbags to cars, fatalities decreased, but they also led us to drive faster, farther, crazier, and talk on our mobile phones at the same time. So safety measures usually work but not nearly as well as we would hope because people just increase their risk (and “utility”) at the same time. In avalanche airbag case, we will also get more powder, more fun, and more risk in the bargain.

The bottom line? Ignore the numbers and focus on terrain and appropriate decision making. My best guess is that avalanche airbag packs will probably save a little more than half of those who would have otherwise have died in an avalanche. They will never save all of them because one out of four will likely die from trauma of hitting trees and rocks on the way down and an additional one out of four will probably end up in a terrain trap (deep burial), buried by a secondary avalanche, or caught in an avalanche that does not travel far enough for the inverse segregation process to work (larger objects rise to the surface).

In addition, people will increase their exposure to risk because of the perception of increased safety, which will cancel out some, but not all, of the effectiveness of avalanche airbags.

As usual, our choice of terrain is far more important than rescue gear. Un-survivable terrain will always be un-survivable. In terrain with few obstacles, terrain traps, sharp transitions and smaller paths, avalanche airbags have the potential to save significantly more than half of those who would have otherwise died. And that sounds pretty good to me.

Bruce Tremper is the director of the U.S. Forest Service Utah Avalanche Center. If you have had an experience with an avalanche and airbag, you can (and should) report it here. To learn more about staying safe in avalanche country, visit the UAC ‘s tutorials.

Photo by Shutterstock

{ 20 comments…read them below or write one }

  • Carson

    “Each gizmo we acquire to increase our safety usually causes us to increase our level of risk at the same time.

    I hear this all the time when discussing avy safety and it certainly sounds like a plausible assumption, but has this phenomena ever been documented?

  • Paul Gerrard

    Carson that’s a good question and the Bruce rightly talks to that exact point. “Risk homeostasis” is a very real thing and I have seen it in many other similar activities and admit to very naturally thinking this way myself. We all have a safety threshold (where the fear starts to take over) and we always back off at that point because it simply stops being fun. With our ability to rationalize things when we add another layer of safety we automatically factor that in and push up to our personal limit again (which is now higher). Not everybody thinks like this but a great majority do who take park in this type of activity. Interestingly this is for the most part done completely subconsciously.

  • steve casimiro

    Carson, it’s been documented many, many times. Seat belts, air bags in cars, helmets on motorcycles, shin guards in soccer…you name it, when people think they’re more protected they take more chances.

  • Rob Coppolillo

    Great post and totally relevant…the risk thing is the crux from an educator’s point of view. I think the bottom line is communicating the notion that avoidance is the only viable solution for avalanches…everything else–especially in places like Colorado, with a shallow snowpack and relatively high tree line–is just Russian Roulette. That said, I own a bag and use it 95% of the time. Like Reagan said, “Trust…but verify.” I’ll avoid, but have my back ups in place in case I blow it!

  • topher donahue

    I’d agree that “risk homeostasis” is a very real phenomenon. Try this if you doubt it: Go backcountry skiing without a beacon for a day and see if you choose the same terrain you would while wearing one. Not really recommended, but if you find your beacon isn’t working during the morning beacon check, you’ll find that it changes your day more than you might think.
    For some documentation of this phenomenon, download this Canadian study on ski helmet use, http://www.skicanada.org/_assets/files/Helmet%20Information%20Nov%202nd%20final.pdf
    and note the conclusion:
    “Although it has been demonstrated that wearing helmets can be effective in reducing the severity of head injuries, Dr. Shealy believes that the increased use of a safety device such as a helmet can alter the behavior of the user, leading to increased injuries. This was demonstrated in the case of bicycle helmets – although usage increased from 18% to 50%, the per capita rate of head injuries increased by over 50%. In his research, he has found that the severity of head injury is higher for helmeted skiers than for non-helmeted. Of helmeted skiers with head injuries, 2/3 are more serious than a mild concussion. For non-helmeted skiers, only 23% of head injuries are more serious than a mild concussion. Helmeted skiers and boarders tend to ski faster.”
    Bruce, great article.

    • Sam B.

      Please don’t get correlation and causation mixed up. You may be preselecting skiers, who are riskier in general, by choosing helmeted skiers. Also historically speaking, the more recent data is usually more accurate. It’s really hard to draw anything but subjective conclusions.

  • David

    Topher thanks for the link. Interesting but other studies have looked at this and come away with different findings. The 2013 NY Times article I linked to states that the majority of research supports helmet usage and doesn’t find increased risk taking.

    If your argument is correct… since the U.S. has mandated lots of safety crap in cars (seat belts/airbags/crumple zones etc) shouldn’t American’s be among the most reckless drivers in the world? My time spent in developing countries (with no seat belts/airbags or prohibitions on bus surfing) suggests that those folks are even more reckless than my raging/texting/road sodaing fellow Americans. So perhaps there is more to it.

    I absolutely do not have the magic answer and it’s totally reasonable of Tremper to bring this up in his discussion of airbags but I suggest this link has not been as convincingly documented as many hold it to be.

  • Graham

    From the Dr. Shealy article (http://www.lidsonkids.org/?p=358), “We cannot say that wearing a helmet makes you ski faster (it may be that people who tend to ski fast are the ones who buy and use helmets).”

    We are looking at a correlation, not a causation.

    Also from Dr. Shealy,”If you are going to wear a helmet, ski and ride as if you aren’t wearing one. Don’t alter your behavior, don’t take more risks or ski or ride faster because you’re outfitted in a helmet. Make sure that you remain in control and ski and ride responsibly.”

    Sounds just like what Mr. Tremper said.

  • Cole

    Thank you for such an informative article. After 3 close friends perishing last year at the same time, I will wear any piece of equipment that will raise my survival rate at all. There is no reason not to have an airbag, the technology exists. Use it. Elyse did and she is alive.

  • topher donahue

    It’s an individual thing. Comparing drivers from different countries is irrelevant. Compare the same driver in a car with safety systems versus a car without, and then the comparison makes some sense.
    With all the safety features in modern cars, Americans may not be the world’s most reckless drivers, but we’re the most reckless we’ve ever been…

  • Joe

    Bruce Temper is a smart guy. Saw him give a presentation once and talked about this same sort of thing. Awesome article

  • Kilgore Trout

    Enjoyable article Mr. Tremper, as is your book. I have to agree Terrain,Terrain,Terrain….makes a diff and makes a slide one thats possibly survivable to one that only through an “act of god” is survivable we tend to embrace the illusion os safety in our culture i believe. All safety gear seems to promote this. Knowledge should be numero uno in the safety bag o tricks however i think any equipment that enhances our chances of returning from our jaunts in the backcountry should be encouraged for it is through its use and documentation that improvements will be made features refined. I have heard that some of the avalanche airbag companies purport their products to be effective in the reduction of traumatic injury any data to support this statement?

  • Greg Franson

    I’ve been reading through this discussion and its been interesting but I believe the real limitation to air bags is terrain. Specifically tree line terrain, where most of our days are spent skiing in North America. The research and statistics that came from Europe come from Alpine terrain. It is a fact that if you deploy your airbag you will be carried further and faster in a slide. You will lose the opportunity to stop yourself and not be carried away through trees and and over cliffs. I have also directly heard from people that were wearing one while involved in an avalanche pulled the “oh shit” handle right away and regretted it as a couple of them were seriously injured and felt they failed to try anything else. They said that once they deployed it was impossible to stop themselves. Its true that the bags may help prevent injury but realize these bags are only made of fabric. I work as a guide in Canada and most all mechanized operations equip there clients with airbag packs. I personally warn my clients of airbag limitations and leave it to them if they want to zip the handle away when skiing into tree line terrain. I’m not speaking against this equipment as it is a great avalanche safety device… the only one designed to prevent you from being buried in the first place. I fully believe it can save your life, I have spoken to many people that have used them (including Elyse) and they are still alive. I just don’t want people to be misguided by statistics without regard to the devices limitations. It should be treated as a last resort but it would take great discipline to not go for the handle right away once involved in a slide.

  • Chris

    “The bottom line? Ignore the numbers and focus on terrain and appropriate decision making. My best guess is that avalanche airbag packs will probably save a little more than half of those who would have otherwise have died in an avalanche.”

    Good enough for me.

  • Greg Fortin

    I agree with Greg and Chris. Knowing the limitations of the equipment, knowledge of safe back country travel and avalanche assessment, and understanding and maintaining risk management in below tree line descents is critical. Airbags will save your life if you are not raked through the trees or over a cliff. Unfortunately as an avalanche rescue technician trauma has played a roll in nearly every fatality I have been witness to. Good education, good decision making, and good group dynamics makes for safe travel. I personally do not utilize the air bag system, I do however dig pits to look for instability, and constantly train to keep my safety skills strong. Keep your tips up and your shoulders to the fall line.

  • Jim

    I agree with Greg and Chris as well. It’s not intelligent to rationalize decisions because you have more safety gear. The bottom line is that you need to be smart in the backcountry. It doesn’t matter how many safety devices you have. Every avy is unpredictable and every avy breaks and behaves differently. Your brain is the best safety device you will find, I promise you. Be knowledgeable and understand that you are often risking a lot regardless of what you have with you. A couple weeks ago, here in Colorado, a couple of college students with beacons and avalungs died in an area that I have skied for years and would have considered fairly safe. We all know the backcountry is dangerous, but we can all be devastatingly surprised by the disasters it is capable of creating.

  • Eric B.

    Like any good avy safety item like beacons, Avalungs, probes and shovels, avy airbags help increase your survival chances in many avy scenarios (but not all).

    BUT… the best safety item is avalanche training. Anything that goes against “best practice” of avy training, regardless of the number of safety items you carry, is incresing your risk.

    So, it’s foolish to carry more safety items if you are going to also take more risks and thus REDUCE your chances of survival. Or is that too logical for stoked BC skiers wanting “one more run”?

    And trees, boulder fields and cliffs in avy runouts negate just about any safety item.

  • Richard

    Fantastic article Bruce.

    People seem happy to spend hard earned time and money on backcountry survival gadgets, which beacon is best, which brand of airbag should I get, do I need an avalung, should I get quick release splitboard bindings? Etc etc.

    I’m certainly not advocating NOT having this kind of gear(sorry about the double negative!), but As jim said, your brain is by far the most important piece of safety equipment in the backcountry and the one I try and spend the majority of my time and money trying to improve (avalanche education, terrain decisions etc).

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