Category Archives: safety

Helmet Design and Environment Interaction

I wanted a new helmet that offered some side-impact protection to replace my trusty Petzl Ecrin Roc, especially after a helmet-less Slovenian climber mocked me in Italy for wearing “such a heavy helmet” at a sport climbing crag.

I now own the Petzl Meteor, but after one trip discovered a strange design flaw.

Most helmets clip together the way carseats or backpack buckles clip together:
clip

The Petzl Meteor helmet has a similar clip, but also contains magnets that draw the buckle together. Here is how it should work:

I was climbing at Lover’s Leap in California, a granite cliff. Those of you who know your geology might guess what happens when you combine magnets and iron-rich granite. I put the helmet on the ground while sorting gear, put it back on and heard the buckle snap together. A few minutes later, I looked down (which put some strain on the helmet strap), the buckle popped open, and the helmet fell off my head.

When I examined the buckle, there was grit stuck to the magnet.

Iron grit on magnet
Iron grit on magnet

Wiping it off seemed to work, except that it moved some of it to the sides rather than just the top. My fingers weren’t small enough to wipe it from the sides. So, the next time I snapped it shut and checked to make sure it was locked, I couldn’t get it off. The grit on the side prevented the buckle from pinching enough to release. I was finally able to get it off the sides by using part of a strap to get into the crevices.

Iron grit on sides

I made some videos of the phenomenon. It was pretty easy to do, I just had to put my helmet on the ground for a moment and pick it up again. Attached grit was guaranteed – these are strong magnets!

I am not the only person to notice this:

In one review of another helmet with a similar closure:

The only issue I had with the buckle came after wearing the Sirocco while bolting and cleaning a granite sport route. Some of the swirling granite dust adhered to the magnets, obstructing the clips. It was easy enough to fix: I just wiped the magnets clean, and it has worked perfectly since.

and:

Helmet review from Outdoor Gear Lab

What we found in our tests of both the Meteor and the Sirocco was that the magnet did not always have enough oomph to click both small arms of the buckle completely closed. About one in four times, only one of the plastic arms would fasten and the buckle would need an extra squeeze to click the other arm in. Another thing our testers noticed was that the magnet would pick up tiny pebbles which would prevent the buckle from fully closing. The pebbles can be easily cleaned by brushing off the exposed part of the magnet, but it adds an extra step to applying the helmet. The bottom line is, we prefer the simplicity of the old plastic buckle. We think that the magnet is a gimmick which potentially makes a less safe helmet.

Safety gear shouldn’t add steps to be remembered, such as making sure the buckle is locked, even after getting auditory and tactile feedback when one connected it. Some people may never climb in an area with iron in the ground, but the use-case for a granite environment should have been considered. You know, for little climbing areas such as the granite cliffs of Yosemite.

Rock Climbing Human Factors – Harness attachment points

A friend of mine was recently rappelling from a climb, meaning that she had the rope through a device that was connected to her belay loop on her harness. As she rappelled, she yelled that her harness broke, and the waistband of the harness slid nearly to her armpits. Fortunately, she remained calm and collected, and was still able to rappell safely, if awkwardly, to the ground. On the ground, her partner saw that her waistband with belay loop had become disconnected from her leg loops. The leg loops were intact, though a keeper-strap that helps the leg loops stay centered was no longer connected.

So, what happened?

First, for the non-climbers, a primer. A climbing harness is composed of three major parts, attached to each other in various ways depending on the manufacturer. The first part is the waistband, which is load-bearing, meaning that it is meant to take the weight of a climber.

The second part of the harness is the belay loop, a load-bearing stitched circle that connects the waistband and leg loops and is also used to hold a belay device, to hold the climber’s weight when rappelling, and for anchoring to the ground or a wall when needed.

The last part of the harness is the leg loops, which are also load-bearing in the parts that connect to the belay loop and around the legs themselves.

Figure 1 shows the general composition of climbing harnesses, with these three parts diagrammed in the Base Concept.

harness_leg_loop_error
Figure 1. Simplified diagrams of climbing harnesses.

On most harnesses, the leg loops are kept connected to the belay loop by a “keeper strap.” This is usually a weak connection not meant to bear weight, but only to keep the leg loops centered on the harness (shown in blue in figure 1). In the case study that prompted this blog post, the keeper strap was connected through the belay loop, rather than the full-strength leg loops (figure 2.) When loaded, it came apart, separating the leg loops from the waistbelt. My own tests found that the keeper strap can be very strong, when it is loaded on the strap itself. But if the leg loops move so that the keeper buckle is loaded by the belay loop, it comes apart easily.

errorharness
Figure 2. Harness assembled with keeper strap bearing weight via the belay loop.

There are two ways to mis-attach leg loops to the belay loop of a harness. The first way is by connecting the leg loops back to the harness, after they were removed, using the keeper strap. The video below demonstrates this possibility. Once connected, the harness fits well and gives little indication the leg loops are not actually connected to bear weight.

The second (and I think more likely) way is by having the leg loops disconnected from the back of the harness, usually for a bathroom break or to get in and out of the harness. The leg loops are still connected in the front of the harness, but if a leg loop passes through the belay loop, suddenly the keeper strap is load bearing when the leg loops flip around. However, the harness does not fit differently nor does it look particularly different unless carefully inspected. Video below.

The non-load bearing parts of the harness are what determine the possibility for this error. In figure 1, some harnesses either do not allow disconnection of the leg loops in back or only allow their disconnection in tandem. When the leg loops are connected in this way, the front of the leg loops cannot be passed through the belay loop. Video demonstration below.

Back to figure 1, some harnesses allow the disconnection of leg loops for each leg. If these are disconnected, a loop may be passed through the front belay loop, resulting in the error in figure 2.

In sum, this error can be examined for likelihood and severity. It is not likely that the error occurs, however if it does occur it is likely it will go undiscovered until the keeper strap comes apart. For severity, the error could be lethal, although that is not likely. The waistbelt will hold the climber’s weight and having leg loops and a waistbelt is a (comfortable) redundancy. However, the sudden shock of suddenly losing support from the leg loops could cause loss of control, either for an un-backed-up rappell or while belaying another climber.

What are the alternatives?

  • Climbing is exploding, particularly climbing in gyms. The “gym” harnesses, with fewer components and gear loops (Figure 1), are a good option for most climbers now. However, there is little guidance about what harness one should buy for the gym vs. outdoor versatility so few probably know this harness is a good option.
  • Some harnesses are designed to be load-bearing at all points (i.e., “SafeTech” below). It is impossible to make an error in leg loop attachment.
  • safetech

  • Harnesses with permanently attached leg loops or loops that attach in the back with a single point are unlikely to result in the error.
  • Many climbers reading this are thinking “This would never happen to me” or “You’d have to be an idiot to put your harness together like that” or my usual favorite “If you wanted climbing to be perfectly safe, you shouldn’t even go.” Blaming the victim gives us a feeling of control over our own safety. However, there are other instances where gear was assembled or re-assembled incorrectly with tragic consequences. No one (or their child) deserves to pay with their life for a simple mistake that can be prevented through good design.

    Short Course in Anthropometry

    NPR just ran an extremely detailed article on the importance and study of anthropometry. The topic is the undue stress nursing places on the spine, even when “proper” lifting procedures are followed. Highlighed is the work of Bill Marras (recent Editor of the journal Human Factors), who developed a sensor rig for the forces experienced by the spine. Read for yourself, but if you want the high points:

    “Moving and lifting patients manually is dangerous even for veteran nursing staff, Marras says, for several reasons:

    • The laws of physics dictate that it’s easiest to lift something when it’s close to your body. But nursing employees have to stand at the side of the bed, relatively far from the patient.

    • Nursing employees also often bend over the patient. That’s important, because there’s a chain of bones along the spine, called facet joints, hidden under the little bumps protruding under the skin. Those bones interconnect and help absorb loads when standing straight. Marras says that when nurses lift as they’re bending, those bones disengage and their disks take most of the force. Those forces are “much, much higher than what you’d expect in an assembly line worker,” he says.

    • When nurses keep working under these loads, it causes microscopic tears in the “end plates,” which are films as thin as credit cards above and below each disc. Those tears lead to scar tissue, which can block the flow of nutrients into the disks — until, eventually, the disks start to collapse. “You could be doing this damage [to your back] for weeks or months or years, and never realize it,” says Marras. “The event that caused you to feel the problem is just the straw that broke the camel’s back.”

    The final conclusion was that people cannot lift other people safely. Assistive machines are needed, and as the article points out, hospitals do not have them.

    Tylenol: A narrow margin of safety

    I’m always surprised at how many people don’t know how dangerous Tylenol (or anything with acetaminophen/paracetamol) is. I can’t remember where I initally learned that just a few pills could cause liver failure, but it was at least 10 years ago. Of course, more than 10 years ago, I remember that Tylenol was the only painkiller allowed to be given out in my high school because it was so “safe.”

    Anyway, it’s certainly been in the news lately and I have collected some interesting sources. First off, This American Life devoted an hour to investigating the problem, its history, and ongoing conflict. Absolutely worth a listen. Here is a teaser bit of the transcript:

    Will Lee is one of the liver specialists and researchers who’s been calling attention to the dangers of acetaminophen. He is at the University of Texas Southwestern Medical Center and talked to reporter Sean Cole.

    Will Lee: In one of the articles, we actually printed up the little coupon that I got with my Zocor prescription that says, $2 off on your next acetaminophen bottle. And one of the things on the coupon, it says safest. Not safer, or not safe, but safest. Well, this is the number-one drug killing Americans every year.

    Sean Cole: Over-the-counter drug killing Americans.

    Will Lee: Over-the-counter drug.

    Sean Cole: Not the safest.

    Will Lee: Not the safest, for sure. So I guess that’s– if you think I have a bee in my bonnet, that’s probably where it came from.

    There are two human factors issues related to this “narrow margin of safety” that I’d like to highlight:

    1. Warning design
    2. Counter-intuitive doses for children

    Warnings

    If you’d like a good overview of warning design, see Wogalter, Conzola, & Smith-Jackson, 2002.

    The warnings are printed in red on the lid of the container and say “Contain acetaminophen – Always read the label.”
    warning
    I know it took a long time to even have this, but I’d like to point out that this does not follow the best practices for warning design because it does not include the consequences or focus on the “hidden hazard.” Hidden hazards are really the reason warnings are important. Here are some examples:
    1. Does a knife need a warning that it is sharp? No, that’s not a hidden hazard. Now, if the knife is SO sharp it’s unexpectedly dangerous, then it needs a warning that conveys that information. I had a friend in high school who had a habit of testing knives with his fingertip. This never cuts you, just gives a feel for sharpness. Well, one time he had someone sharpen a swiss army knife for him – and what usually would have “felt sharp” went instantly through the skin down to the bone. That’s a hidden hazard.
    2. Does coffee need a warning that it’s hot? No, not if it’s just drink-ably hot. But yes if it is purposefully super-heated enough to cause 3rd degree burns. Watch this video to get new insight on the McDonald’s coffee story.

    It is the narrow margin of safety that is the hidden hazard of acetaminophen. Nothing else available over the counter can kill you with such a small increase in dose. You can take 20x the recommended dose of Advil before it becomes threatening. I ignored the dosing for Advil once and took 6 in 3 hours rather than 2 – it made me sick and I regretted it, but would I deserve to die for that mistake? I could have died if it had been Tylenol instead of Advil. This hidden hazard is the most critical part of the warning – even if it’s on the label, I think it should be highlighted on the lid.

    Which brings me to… the hidden hidden hazard that was created by the Tylenol company.

    Counter-intuitive doses for children
    In brief, for over a decade Tylenol provided medication labeled for infants and medication labeled for children (and of course, medication for adults). 99/100 people on the street would assume that these were in order of strength – least for the infants, more for the kids, and most for the adults. That assumption was correct for the kids and the adults. The counter-intuitive dose was for the infants: instead of being weaker because they were smaller, it was much higher. Their reasoning was that it is hard to get medication into an infant, so if it’s stronger you can get an effect with less. An article from Pro-Publica gives a more detailed summary.
    An excerpt from Pro-Publica:

    The two types of pediatric Tylenol had a counterintuitive difference. Drop for drop, the strength of Infants’ Tylenol far exceeded that of Children’s Tylenol.

    In addition, the active ingredient in Tylenol, acetaminophen, has what the FDA deems a narrow margin of safety. The drug is generally safe at recommended doses, but the difference between the dose that helps and the dose that can cause serious harm is one of the smallest for any over-the-counter drug.

    By confusing the pediatric products and administering too much of the infants’ version, parents could inadvertently overdose their children. Other manufacturers also made two children’s products with different concentrations of acetaminophen.

    Between 2000 and 2009, the FDA received reports of 20 children dying from acetaminophen toxicity – a figure the agency said likely “significantly underestimates” the problem. Three deaths were tied directly to mix-ups involving the two pediatric medicines. Such errors may have caused some of the other deaths, but the agency has acknowledged that its data lacks sufficient detail to determine the precise cause.

    This American Life included a heartbreaking case where parents were instructed to give their infant doses measured in terms of the children’s Tylenol (their doctor just said “Tylenol”), but since they had an infant they did what anyone would and used the Tylenol for infants, resulting in the death of their baby.

    The big push seems to be for better warnings (with the example in the picture as “better.”) Indeed, this can have an impact – for example, as reported in the NY Times, removing infant versions of medication and saying a drug is “not for children under 2” reduced drug-related emergency room visits for that age range by half.

    Excerpt from the NY Times article:

    In 2007, amid mounting concern that infant cough and cold medicines were unsafe and misused, manufacturers voluntarily withdrew products intended for children younger than 2. The makers revised the labels on the rest of the medicines, which now warn parents that they should not be given to children younger than 4.

    Government researchers said on Monday that those moves have had a remarkable effect: a significant decrease in emergency hospital visits by toddlers and infants with suspected medical problems after using these medicines.

    Dr. Daniel Frattarelli, a former chairman of the committee on drugs at the American Academy of Pediatrics, praised the study, saying it showed that “the label is a very powerful tool for changing parent behavior.”

    In the new study, published in the journal Pediatrics, researchers at the Centers for Disease Control and Prevention reviewed data from 63 hospitals to estimate the number of emergency visits from 2004 to 2011 by young children who had taken cough and cold medicines.

    Children under 2 accounted for 4.1 percent of all emergency visits for suspected drug-related effects before the 2007 withdrawal, the researchers found, and accounted for 2.4 percent afterward.

    However, even casual readers of the blog have probably noted how often I mention the Hierarchy of Safety: first try to design out the hazard, guard against the hazard, and warn. I’m not saying warnings aren’t important, but if we want to have the biggest impact we should be working on designing out or guarding against the hazard. Some ideas in that realm include bottle design that restricts the flow of liquid (this could prevent a child from dosing him or herself, but not parents from giving the wrong dose), and packaging “single servings” of medication, so that its obvious how much to give at one time. Although the treehugger in me isn’t a fan of more packaging, this also could provide more space for good warnings AND have those warnings in extremely close spatial and temporal proximity to use of the product.

     

    Brilliant guard against accidents in indoor rock climbing

    For those who don’t follow news of climbing accidents as closely as I do, there has been a spate of accidents associated with the automatic belay devices (autobelays) installed at climbing gyms.

    These devices are handy to have around as they negate the need for a climbing partner, allowing one to exercise and train alone. The climber clips his or her harness into the device at the bottom of the wall, and it automatically retracts (like a seat belt) when you climb upward. At the top, you let go of the wall and the device lowers you slowly back to the ground. You are probably imagining that the accidents had to do with failures of the equipment – while that is not unheard of, the most recent issues have all been with climbers forgetting to clip into the system at all.

    The most recent tragedy occurred this past September, where an experienced climber died after a fall in a Texas gym, and it’s been listed as so common it happens at “every gym,” though not always resulting in a fall. Here is the facebook page with members of another gym discussing a similar accident.

    fb

    If you talk with climbers or read accident forums you will invariably be faced with a large contingent bent on blaming the victim. I’ll grant that it is hard to imagine forgetting to clip into a safety device and climb 30 feet up a wall, but that’s because I hardly ever do it. One characteristics these accidents share is that the victims were experienced and used the auto-belays frequently.

    When a procedure becomes automatic, it becomes more accurate and less effortful, but it also becomes less accessible to the conscious mind. When a step is skipped, but all other steps are unaffected, it’s especially hard to notice the skipped step in an automatic process. If caring more or working harder or “being more careful” could actually prevent this type of problem, we wouldn’t have any toddlers left in hot cars, perfectly good airplanes flown into the ground, or climbers falling because they didn’t clip into the autobelay.

    That brings me to the device I saw installed at a climbing gym last night.

    guardAbove: The guard in place, clipped to the wall and ready to go. Notice how it blocks the footholds of the climbs.

    photo 2Above: Nikki shows how to unclip the guard before attaching to her harness.

     

    photo 4Above: Clipped in and safely ready to go. Guard is on the ground and out of the way (it is ok to step on it!)

    Let me tell you why I think this is brilliant.

    • It’s highly visible.
    • It functions as a guard. This adheres to the hierarchy of safety: First, try to design out the hazard. Second, guard against the hazard. Last, warn. These are in order of effectiveness. Prior to this device, I had only seen signs on the wall saying “Clip in!” (And a year ago, even those didn’t exist.) This device physically blocks the start of the climbing routes, demanding interaction before one starts climbing.
    • Using it properly does not add any additional time or mess to climbing a route. If it weren’t there, the climber would still have to unclip the autobelay from an anchor close to the ground, etc. With it there, the climber does the same thing and once done, the guard becomes a flat mat that doesn’t get in anyone’s way.

    Is it perfect? No. You can also climb with a belayer on the same or nearby routes, and then it’s also blocking your way at the start of the climb. Some adaptation should be made by the route-setters at the gyms to minimize this. But overall, what a great and simple solution.

     

    Potpourri–Lazy Summer Edition

    It’s summer and we (along with some of you) are taking a break.  But here’s a list of interesting usability/HF-related things that have crossed my path:

    • After much complaining, Ford is bringing back physical knobs in their MyTouch in-car controls.  Anne and I worked on some research (PDF) in our past lives as graduate students that directly compared touch-only interfaces to knob-based interfaces so it’s nice to see it is still a major issue; if only Ford read our 9 year old paper 🙂
    • Trucks driving under very low bridges is such a large problem in Australia that they are deploying a really novel and clever warning system.  A waterfall that projects a sign that’s hard to miss!
    • tags_finderApple will introduce their next version of OSX in the fall. One of the features i’m most excited about is system-level tag support.  Tags allow users to organize their files regardless of location or type.  I’m particularly interested in personal, single-user-generated tagging (compared to collaborative tagging like that used in flickr) as it appears to benefit older adults information organization and retrieval (PDF).  This pleases me.

    Recent developments in in-vehicle distractions: Voice input no better than manual input

    A man uses a cell phone while driving in Burbank, California June 25, 2008. Credit: Reuters/Fred Prouser
    Earlier this week the United States Department of Transportation released  guidelines for automakers designed to reduce the distractibility of in-vehicle technologies (e.g., navigation systems). :

    The guidelines include recommendations to limit the time a driver must take his eyes off the road to perform any task to two seconds at a time and twelve seconds total.

    The recommendations outlined in the guidelines are consistent with the findings of a new NHTSA naturalistic driving study, The Impact of Hand-Held and Hands-Free Cell Phone Use on Driving Performance and Safety Critical Event Risk. The study showed that visual-manual tasks associated with hand-held phones and other portable devices increased the risk of getting into a crash by three times. [emphasis added]

    But a new study (I have not read the paper yet) seems to show that even when you take away the “manual” aspect through voice input, the danger is not mitigated:

    The study by the Texas Transportation Institute at Texas A&M University was the first to compare voice-to-text and traditional texting on a handheld device in an actual driving environment.

    “In each case, drivers took about twice as long to react as they did when they weren’t texting,” Christine Yager, who headed the study, told Reuters. “Eye contact to the roadway also decreased, no matter which texting method was used.”

    Begging robots, overly familiar websites, and the power of the unconscious?

    Hello readers, and sorry for the unintentional hiatus on the blog. Anne and I have been recovering from the just-completed semester only to be thrown back into another busy semester.  As we adjust, feast on this potpourri post of interesting HF-related items from the past week.

    In todays HF potpourri we have three very interesting and loosely related stories:

    • There seems to be a bit of a resurgence in the study of anthropomorphism in HF/computer science primarily because…ROBOTS.  It’s a topic I’ve written about [PDF] in the context of human-automation interaction.  The topic has reached mainstream awareness because NPR just released a story on the topic
    • The BBC looks at the rise of websites that seem to talk to us in a very informal, casual way.  Clearly, the effect on the user is not what was intended:

    The difference is the use of my name. I also have a problem with people excessively using my name. I feel it gives them some power over me and overuse implies disingenuousness. Like when you ring a call centre where they seem obsessed with saying your name.

    Product Confusability: Tide Pods

    Kim Wolfinbarger sends along a new case of dangerous things being confused for food (the story is the same but the actors different, see previous examples).  Before you reflexively say, “only an idiot would confuse the two,” remember that 5-year olds don’t know the difference.  First rule of HF-club: you are not the user (or victim):

    In California alone, 307 cases of accidentally ingestion of laundry packs by young children have been reported this year. And the cases in California, and nationwide, aren’t just limited to toddlers snarfing Tide Pods. When the product was released, Tide rivals such as All and Purex launched their own single-dose detergent capsules as well. Earlier this summer, Tide reconfigured the packaging of the product, adding a double-latched lid to the plastic tubs containing the Pods to make it more difficult for children to tamper with. Still, the number of reported incidents continues to climb along with news stories warning parents to take caution.

    Just yesterday, Consumer Reports reported on a wave of Tide Pod-related poisonings in Glasgow, Scotland while the New York Daily News published a quick article stating that in New York City alone, 40 children have been hospitalized after eating the packs since April. TODAY also just published a piece on the alarming trend in which Ken Wahl, medical director for the Illinois Poison Center states: “I’ve never seen a consumer product that had that degree of injury in a child.”
    Dishwashing detergent also comes in pod-like single serving doses but I am not aware of similar cases of ingestion.  Maybe it’s the coloring (they tend to be blue/green) or size (they are a bit larger I think)?