Category Archives: affordances

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:

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.


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.

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.

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.

    Haikuman Factors

    Sometimes it’s good to take a step back from the seriousness of our work and find new focus. H(aiku)man factors is the brainchild of my colleague Douglas Gillan. Each summarizes a concept in the field while following the haiku form of 5-7-5 and an emphasis on juxtoposition and inclusion of nature. Enjoy and contribute your own in the comments!

    H(aik)uman Factors3

    H(aik)uman Factors2

    H(aik)uman Factors

    H(aik)uman Factors6

    H(aik)uman Factors5

    H(aik)uman Factors4

    All of the above are by Doug Gillan.

    Other contributions:

    Inattentional blindness by Allaire Welk
    Unicycling clown
    Challenging primary task
    Did you notice it?

    Affordances by Lawton Pybus
    round, smooth ball is thrown
    rolls, stops at the flat, wing-back
    chair on which I sit

    Escalation by Olga Zielinska
    headache, blurred vision
    do not explore Web MD
    it’s not a tumor

    Automatic Processing by Anne McLaughlin
    end of the workday
    finally get to go home
    arugh, forgot groceries

    Automation by Richard Pak
    Siri, directions!
    No wait, I’ll get it myself
    Drat, I forgot how

    Prospective Memory by Natalee Baldwin
    I forgot the milk!
    Prospective memory failed
    Use a reminder

    Working Memory by Will Leidheiser
    copious knowledge.
    how much can I remember?
    many things at once.

    Worst Mobile Interface Ever

    I was reading articles the other day and came across a site that, as many do, reformatted for my phone. Almost all reformatted-for-mobile sites are terrible, but this one is my favorite.
    You cannot scroll through the 21 page article by moving your finger up and down, as would happen on a website. The only way to change pages is via the horizontal slider at the bottom. Good luck trying to move it so slightly it only goes forward one page! And yes, moving the slider left and right does move the page up and down.

    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.


    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.


    User Testing for Interplanetary Expeditions

    I was listening  to the Big Picture Science podcast on my way to work this morning when I heard  a great example of how to test equipment prior to a mission. Hosts are Molly Bentley and Seth Shostak.

    The interview was with Dr. Jennifer Heldmann, an astrobiologist who studies “Mars analogues” on earth – the Atacama Desert in South America and the very cold, very dry “dry valleys” in Antarctica. Her main purpose is to investigate whether (and what kinds of) microbial life can survive in these conditions, but she also tests the methods we might use to collect samples from other planets. Here is a transcript describing a usability test in  “A Martian Curiosity”:


    Bentley: Well Jennifer, I was looking at a picture of you in a spacesuit. And you were standing in an alien land, and I’m pretty sure it wasn’t Mars, and it wasn’t even the moon. Where were you?

    Heldmann: That could have been a number of places, I’ve worn spacesuits in a variety of places. All on Earth, I might add. Because we do a lot of work here on Earth to study and learn how to go and operate on other planets. So, for example, I would love love love to send people to Mars, so we can explore that planet, it’s really hard to do that, though. And we have to learn “how do you live on Mars?” “How do you work on Mars?” “How do you talk to people back on Earth from Mars?” And so, to answer those really important questions, we go out and we test it. We go to places on Earth that are like Mars. Mars is really really cold and Mars is really really dry, and so we go to cold and dry places.

    Bentley: Can you share with us a story about what it’s like to walk around in some of these environments with a spacesuit on? Anything that surprised you?

    Heldmann: Yes, there was one time out in Utah, we were at the Mars Desert Research Station, wearing a spacesuit, and we had a camera crew with us, because there was a group doing a documentary about Mars analogues and working out in Mars. So we said “sure, come with us, we’re going to do an EVA, an Extra Vehicular Activity, which means we’re going to wear our spacesuits and walk around, and get some rocks, and get some samples, great, come out with us. So we had little sample bags, and we had them in our backpacks, and we had our spacesuits on, and we get to the rock outcrop, and we pick up the rocks. And these are great, these are just what we were looking for, we’re all excited, and then we go to put the samples in the bag and we couldn’t get the bags open. Because we’re wearing these big, thick gloves.. you don’t think about this ahead of time! You just think “oh I’ll open the bag, and I’ll put the rock in. How hard is that?” It’s really hard when you have a spacesuit on.”

    Bentley: What were they, like a ziplock bag or nylon mesh? Velcro? What was it?

    Heldmann: Yes, it was a ziplock type of thing. You just had to pull it apart. Really simple, we do it every day in the kitchen, right? But with those big, thick gloves on we could not get our sample bags open. It was very embarrassing to have a film crew watching you for hours try to open a ziplock bag. It would have been really simple to just take the glove off and open the bag, but on Mars you can’t do that.

    Bentley: And it would have been a bummer to go to Mars and find great rocks and then not put them into a bag and bring them back.

    Heldmann: Exactly!


    Then, to my delight, later in the podcast the hosts took it upon themselves to make an analogue of the equipment used in the Mars mission analogue and do a think-aloud. (18:01)

    Bentley: Seth, could you put on those oven mitts that I set down in front of you, please?

    Shostak: Why, are we getting some pizza out of the oven? What’s the deal?

    Bentley: Ok. So you see what else I put down there, in front of you?

    Shostak: Yeah, this giant ziplock bag.

    Bentley: Yes, this may be the largest ziplock back I’ve ever seen. It’s almost a body bag size.

    Shostak: I was almost going to say “Did you order this from ‘Mafia supply company'”? What do you want me to do with this bag?

    Bentley: It’s closed, right now. Jennifer was trying to open a ziplock bag, she said, while she was in the desert, and she wasn’t able to do it for the cameras. What I want you to do is open it and describe what you’re doing. Now, you have oven mitts on .

    Shostak: Well, actually it isn’t too hard to open this, if you want to know the truth, because it’s so big that even with oven mitts.. watch. (crinkle sounds) Maybe it’s not so easy. Pull it!

    Bentley: C’mon, Seth! The Martian rocks are waiting for you. (struggling sounds)

    Shostak: Well, those Martian rocks are safe from me because I cannot get this bag open!

    Bentley: Ok, Jennifer is vindicated.

    Oven mittens or something similarly cheap could be a nice lab-based pre-test for any manual equipment, before it even gets to the spacesuit test.

    So.  In closing…  Human Factors isn’t rocket science.

    Or is it!?!?



    Photo credit veggietothemax @ Flickr

    No one wants to touch the gas pump


    The above is from a gas pump in a large metro area. Can you guess the most common zip code number? How about what object people use to to press the keys?
    But you’re probably missing my favorite part – look in the lower right. Do you see the black electrical tape? Under that tape is the START button for the gasoline. The instructions on the screen say to “press the start button to begin fueling.” As the most commonly pressed button it was the first to be destroyed, and the station attendant’s tape solution earned it a humor tag in this post. I’m also willing to bet that hiding the START button is why the “No/Cancel” button has been furiously destroyed as well.

    I’ve come across some of these where the soft keypads were entirely destroyed by keys for the common zip code numbers. Once I had to leave to find another gas station, since it wouldn’t accept my card without a zip code entered and the buttons no longer worked.

    Photo credit Maribeth Gandy Coleman

    Innate number sense changes with age

    New research shows that our ability to rapidly estimate the number of things in a set (an ability called subitizing) peaks around 30 and declines with age.  Researchers posted an experiment online to measure this “number sense”.

    This could have implications for the design of displays that require decision making based on judgements of the number of things.  A simple example might be comparing the star ratings on products when shopping online.

    The team found that scores on the test improved gradually throughout the school years, peaking around age 30, then declining. Nonetheless, there were large individual differences in scores among people of the same age. Those differences appeared to be modestly linked to school performance: Those with the best innate number sense reported the highest ability in math in school. A subgroup of nearly 500 subjects were also asked to report their math scores on the SAT. Again, a higher innate numbers sense was associated with higher SAT scores.

    Lack of human factors = more of your tax dollars at “work”

    I live in Raleigh, NC. Our area code has always been a little problematic for the nationwide 911 emergency system – it is 919. But at least until now, dialing the 919 for a local call was optional. Looks like we’re finally big enough for ten digit dialing and we can expect to pay the price in our public safety system.  Check out this email from the Director of Emergency Communications, particularly the part about dispatching officers every 7.5 minutes to investigate hang-ups:

    I am sure by now that you have seen or heard about some of the impact that the new 10 digit dialing requirement has made upon our 9-1-1 center. Unfortunately, we are almost three weeks downstream from this implementation, and are seeing few signs of improvement.

    Neither the 9-1-1 center, the city, or the local telephone carriers are responsible for selecting area codes. They are distributed according to a national plan. “Overlays” are added when a region begins to run out of numbers in their original pool; in this case 9-1-9. Unfortunately, with the similarity between 9-1-9 and 9-1-1, our agency has seen this issue in the past, as some of our citizens have utilized 10 digit dialing for some time. The current impact on our staff – and on law enforcement – is that on our peak days we are dispatching officers to investigate hang up calls once every seven and a half minutes. Of course, this is a daily average, meaning that at peak times the impact is even more severe. Plus, we only dispatch calls that we can’t resolve another way. Many people who misdial don’t realize they have until we answer. Others hang-up, but answer when we call them back. In such cases sending an officer is not required, so the total number of calls we receive in error far exceeds those dispatched.

    As Director of Emergency Communications, I am asking for your help. We have identified that a majority of such calls come from either senior citizens or business telephones. In the first case, confusion over the proper procedures seems to be the norm.  After 40 years, folks now have to dial 10 digits just to talk to their neighbor. We’ve had callers tell us they thought they had to now dial 9-1-1 before calling in our area, and others ask if they needed to dial 9-1-9 before they called 9-1-1. If you have an elderly friend, relative, or neighbor, I’d like to personally ask you to take the time to make sure they understand to carefully dial “9-1-9” when required. I believe that with some patience and understanding we can make significant inroads.

    With regard to business telephones, the issue is a little more complex, and may in some cases even involve the need to dial “9” to get an outside line, followed by the unnecessary “1” before dialing the area code. Whatever the reason, it really boils down to just taking a few extra seconds to make sure of the numbers you’re dialing. Whether you work at a local business, or own one, can I please also count on you to assure that your co-workers use due care when calling? This is a very serious issue and takes resources away from dealing with actual emergencies.

    So, to summarize:

    • There is a lack of understanding when to use 10-digit dialing.
    • Being “careful” is not going to fix this problem.
    • The added traditions for businesses to dial “9” to get out adds to the problem (NC State moved to a dial “7” system, presumably for this reason).
    • Those with a lifetime of 7-digit experience, and presumably the least likely to have numbers pre-programmed into a cell phone, make the most errors.

    The issues here are fascinating, yet predictable. I don’t know if there is a perfect answer, since changing the long-term ill-chosen area code would be confusing (although my home town in Alabama has gone through 3 such changes in the last couple of decades – from 205 to 334 to 251!). But it is clear that we are penalized by the similarity of our numbers to a national standard for emergency calls. I applaud the tone of the email, which is not blameful – just desperate for a solution. However, I have great skepticism that advising “due care” in dialing will make any difference at all.