Georgia Tech Research Institute

Feedback (2 of 2)

Issue: System response time to user input is slow.

Users rely on timely feedback from the system in response to their inputs. If feedback is not provided in a timely fashion, users may conclude that their input was not accepted and try again, leading to multiple activation errors. This is a usability problem for all users, but it may exacerbate difficulties for users who are more prone to making input errors (e.g., users who are blind or who lack fine motor control).

Populations Impacted: Users who are blind; users with low vision; users with upper mobility impairments.

Potential Solutions:
  • Minimize system response lag time. The system should provide timely feedback to the user. The system should provide some response to user input within 500 ms. If the system response to a user input takes longer than 500 ms, an interim "in progress" indication should be displayed to acknowledge that the input was received and is being processed.

  • Allow easy recovery from errors. A "Back" or "Undo" button should be provided to allow users to recover from multiple activation errors or accidental inputs. Note that a button labeled "Cancel" is somewhat ambiguous; a user may think that a "Cancel" button will cancel the entire transaction, rather than cancel only the most recent input.

  • A confirmation screen on an airline check-in kiosk shows that the user accidentally indicated that he wanted to check 22 bags.  A back button is provided so that the user can return to the previous screen and correct the error.
Applicable Guidelines:
Section 508 - 1194.25(b), 1194.31(f)
HFDS - 2.6.1,,,,,,