The Edge Case Usability Conundrum


A Usability quirk that is going to get me arrested one day

My blackberry has a button for “Place Emergency Call” on the front screen when the device is locked.  I can understand why it doesn’t require unlocking the device with my password to use it. Perhaps I’d need to call 911 using my elbows in the event that  severed all my fingers.

However, the downside is that I have more than once “pocket-dialed” 911 and recently while grabbing the phone, accidentally mashed some of the buttons, and it made a previously unfamiliar strange kind of beep. The display said “Emergency Callback mode” to which I freaked out and pulled the battery out so the cop couldn’t find his way over to tase me.

Insufficient Idiot Proofing

My first instinct was to write critical post about the poor UI design, but as proof of my subtle progress towards maturity as a blogger, and the fresh lessons learned from my overly hasty with criticism of DVD authoring software,  I took a step back and looked at the issue more objectively.

The authors of the BlackBerry firmware did put some effort into addressing the accidental 9-1-1 call.

  • Confirmation prompt must be dismissed before Emergency call is placed.
  • The default is “No” on the confirmation prompt.
  • It makes an obnoxious and distinct tone when you start an Emergency call.
  • The screen clearly displays “Emergency Callback Mode” when dialing so you don’t have to know the meaning of the auditory warning.

In the case of my button mashing, these precautions were effective. They alerted me the situation and guided me without confusion to a course of action to remedy the situation. However, it isn’t hard to come up with scenarios that could easily thwart these protections:

  • Pocket Dialing in a noisy environment
  • Child/Pet playing or chewing on the phone

Apparently I’m not the only clutz in the word either:

Suggested Design Improvements

Conflicting requirements is a key reason why it is so difficult to design effective Human-Device interaction. Here, the device needs to provide quick and easy access to the emergency call function while making it difficult to accidentally trigger it.

In this case it is clear to see that a compromise was necessary and the downside of not being able to get help in an emergency was clearly worse than an inadvertent emergency call, though still objectionable.  However, I do still see some room for improvement.

Idea 1:  Add a dedicated emergency call button to the physical device with a sliding door that clicks closed

Whenever the consequences of accidental activation of a feature are especially undesirable, I prefer a strong forcing function to a weak one like a confirmation dialog. Overloaded controls are inherently weak implementations of forcing functions because they don’t zap the user into a higher state of awareness that is necessary for doing big scary things.

That is exactly why the launch missile buttons have little acrylic covers on them. Unlike hitting a Y or N in response to a confirmation prompt, which the user is likely to blaze through out of habit because they have been pecking at they keyboard all day, the need to open the cover forces the user to engage in an activity that is markedly different to jar their brain into an attentive mode. Launch Button

This also works well, for prevention of accidental activation, which makes it relevant to the emergency call feature of the cell phone. In fact, I’d argue that it is a good fit whenever the following are true:

  • Very Undesirable Consequences
  • Infrequent need to activate functionality.

Idea 2: Get Rid of the Keyboard Shortcuts on the Confirmation screen

Shortcut keys have a very specific purpose, to speed up frequently used operations and thus make the operator more efficient. For the hypochondriac or drama queen, perhaps I would recommend a JitterBug or LifeAlert device instead. Adding multiple ways to confirm a function with big consequences is just asking for trouble.

Idea 3:  Make it vibrate when initiating an emergency call

This helps to solve the problem of pocket dialing in a noisy place.

Idea 4: Add a ten second countdown after activating emergency call mode

This would give the user time to react to the beeping and vibrating device and abort before any damage is done.