The link between usability & accessibility.

Coming home on the train this week, the frantic behaviour of a woman who was visually impaired highlighted some important aspects about accessibility, usability, design changes and user behaviour.

Consider the location of a button on a train door.  This button is always located on both sides of the door in both older and new train carriages. (see 1 below) The button located beside the door is the most familiar and logical location for the button.  However, in recent times, some of the older train carriages have been refurbished. It appears that the designers / engineers believed they would improve the usability of the internal door buttons by moving the button from beside the door to the end of an adjacent internal partition about 70 cm away from the original location. (see 2 below)

Usability flaw in the everyday design of a train

Design changes to improve usability?

In recent years, trains have become increasingly overcrowded with more people choosing to commute on public transport. Maybe the rationale of the design change was to improve the usability of the door button for commuters owing overcrowding problems on trains.  Changing the location of the button would improve usability in this context by:

a)      Providing easy access for able bodied commuters in a crowded train carriage. The new location of the button did not require commuters to push their way through a crowd to open the door if the button is more conveniently located on an internal panel within the carriage.

b)      Improving the access for disabled commuters.  The seating directly behind the internal panel is reserved seating for elderly and disabled commuters.  Moving the button to the internal panel improves the accessibility of the button to disabled or elderly commuters seated in the reserved seating.

These reasons appear to be logical rationale to change the location of the button to enhance the user experience of all commuters.  To communicate the design change, large signs have been placed in the original button location with arrows indicating the new location of the door button (see 1 above).  The behaviour of the button when the train comes to a stop also reinforces a visual cue to highlight the change in location.  When the train stops, the buttons flash with bright neon green lighting and emit a loud continual beeping noise to attract a commuter’s attention.  These visual cues are appropriate for most commuters, however as I had witnessed, the cues were definitely not sufficient enough for someone with a vision impairment.

Impact on commuters with vision impairments.

Whilst the new location of the door button may be considered or ‘assumed’ to be more accessible to commuters, it is certainly not accessible for commuters with vision impairment.   The woman I witnessed attempting to open the door at her stop, appeared panicked when she could not find the door control button.  She was frantically searching with her hands to locate the button or even to locate Braille instructions to help guide her.

Amazingly, despite all the signage to highlight the change in the button location, the sign located in the normal button position (refer to 1 above) did not include Braille instructions to communicate this change efficiently to commuters with vision impairments.   Braille was included in all other signage on the train, even on button in its new location (refer 2 above).

The woman’s behaviour when she could not find the button in its familiar location also highlighted a very important consideration about user behaviour in stressful environments.  She became quite distressed when she could not locate the button or Braille.  In her panic, she was unable to listen for the consistent beeping of the button when the train came to a stop.  When I reported this incident to a staff member of the rail network, his response was “But couldn’t she hear the button beeping?  I assumed she would find the button because of the beeping. That’s why the buttons beep you know!”

Accessibility & Usability are linked

Historically, accessibility and usability have been viewed as separate issues.  This was a product of accessibility in design focussing purely on accommodating people with disabilities rather than the basic principle of accessibility that asserts designs should be usable by people of diverse abilities, without special adaptation or modification.

The example of the door button location is a good example of the close link between accessibility and usability.   The new location of the door button may have improved the usability of the button for most commuters by enhancing accessibility of the buttons location. However, the usability of the button for vision impaired commuters was seriously impacted by a flaw in accessibility.

Accessibility characteristics and usability.

If you assess the new location of the door button from the context of accessible design characteristics, the flaws in the button design become clear.  Accessible design is characterised by perceptibility, operability, simplicity and forgiveness.

1. Perceptibility:  Can all the commuters perceive the design of the door button regardless of sensory abilities?  In this case, the button location may have been positioned closer to seats for reserved for disabled users; however there is no supportive Braille text in the normal, familiar location of the button beside the door.
2. Operability: Can all the commuters use the design, regardless of physical abilities?  In this case, affordance is impacted because the button has been moved from a familiar location without assistive Braille to communicate the change in location.
3. Simplicity: Can everyone easily understand and use the design regardless of experience, literacy or concentration level?  I believe the signage in the photo above seems too complex just to communicate the location of a door button!
4. Forgiveness: Does the new location of the button minimise the occurrence and consequence of errors?  Once again, affordance is the main issue with the new location of the door button.  In addition, the design offers no constraints or controls to ensure that the button is used in the correct manner and prevent errors occurring.

If all the characteristics of accessible design had been addressed by the engineers / designers, then they may have modified the location of the button so that it is truly usable by people of diverse abilities without special adaptations or modification.

Tags: accessibility, australia, Design, forgiveness, operability, perceptability, simplicity, Usability