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USABILITY AT 30,000 FEET

On a US Airways 767 flight from Los Angeles, I got a close-up view of passenger confusion.  It all started after the meal.  Seated next to one of the lavatories, I had the opportunity to observe and chat with passengers intending to use that facility.

My first inkling about the challenge of getting into the lavatory was from a very nice woman who, when I first saw her, was standing opposite my seat waiting her turn.  We chatted about the two cups of coffee she had consumed and the wonders of Hawaii, where she had just vacationed.  After 10 minutes with no one emerging from the lavatory, she tried the door and it opened.  No one had been in the stall.  She sheepishly leaned over and said, "I had been trying to pull on the door instead of pushing it open."  Then she disappeared into the lavatory.

Her experience prompted me to put on my spyglasses to see if the next person who approached the lavatory would have the same problem.  It wasn't long before a man entered the observation zone.  This was fortunate because I would now have a diverse sample of the passenger population!  Depending on his behavior, I could draw conclusions about the differences or similarities of female and male behavior when entering an airplane lavatory.

The lavatory was empty and as Mr. Man got close to the lavatory door, I was tempted to give him a tip about opening the door so he would have no trouble.  That way my data would show men were clearly superior at the task of entering an airplane lavatory.  However, my instincts to do an unbiased study overcame my desire to come home to my wife, two daughters, and female dog with a story of male superiority.  Peering through the middle portion of my spy glasses (so the bifocals on the bottom wouldn't blur my view), I saw him look at the door and then stand back as if in a waiting mode. I was extremely disturbed when the passenger seated across the aisle interrupted my experiment and told Mr. Man, "There's no one in there -- just push the door."  He explained to her, "I saw the light on," and quickly went inside.  When he came out, I decided not to interview him to get details of his entry dilemma, so I can only speculate on what actually happened -- why he saw a light and how that made him think someone was occupying the stall.

By now I was totally intrigued with this critical problem facing my fellow passengers.  I decided to keep my spyglasses on and observe their lavatory entry behavior rather than catching up on my intended reading and planning.  True to the form of earlier users, most of the eight additional people I saw seemed unsure if the lavatory was occupied and how to try the door.  Again I chose not to interview them to discover the source of their confusion, so I decided to use the lavatory myself.

As I suspected, my fellow passengers were not stupid.  A close inspection of the door clearly revealed that its designers had never before used a lavatory -- at least not on an airplane!  Three major flaws made it confusing to use.

bullet First was the way I was told whether or not the lavatory is occupied.  A small recessed area showed a green circle with a white horizontal line through it.  I reached in and moved the locking lever on the inside of the door while I kept my eyes on the recessed area.  The green graphic moved away and was replaced by a red circle with a vertical white line through it.  Except for two users who had spoken in English, I don't know what languages the others spoke.  Perhaps they understood these "universal graphics," but I wouldn't bet on it.
bullet The second flaw: On the right-hand panel of the bifold door is a beautifully designed aluminum handle.  Of course, a handle is for pulling, which is what most people tried to do!
bullet  The third culprit in this design crime is the word "PUSH" engraved into the aluminum surface just above the handle.  Stopping to read an instruction is not typically the first thing people do when using a door.  (It's the old story about pushing on a door and then noticing the "pull" label)  In this case it is even less likely because the word is well below eye height, is not distinguished in color or surface texture from the rest of the handle plate, and has very little light shining on it because the user stands between the overhead light and the handle.

Author's Note:

Since conducting the previous research, I have more recently traveled on a United 777 flight where I had the chance to repeat the study.  I also was seated opposite the lavatory (is there a pattern here?) and this time the results were different.  Observation of a much larger sample size found that all but three people could easily open the bifold door.  The reason for the high success rate - a more ergonomic design.

bullet The words "occupied" and "vacant" appeared along with symbols
bullet The word "PUSH" was printed in large black letters on an aluminum plate just below eye height
bullet Users approached the door without blocking the light

Interestingly, the three people, who were momentarily confused, initially tried to open the door by pulling out the waist-high ashtray placed on the door to extinguish cigarettes before entering.  The ashtray was shaped like a handle.

This experience of observing first-hand how Human Factors can make a difference has kept the voyeuristic Human Factors fires burning inside of me.  My next project will be to ride the elevators in a tall building and count how many people get off when the door opens -- even though it isn't their floor!

Stan Caplan

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