Guideline summary

Single-access to a function means that operators have only one way to activate a function.

  Considerations in overloading a control with  scenario-dependent or situation-dependent functions include:

• Multi-access function activation enables flexible user control but is error prone. Whenever possible, avoid multi-access to reduce the rate of risky user errors and facilitate skill acquisition.

• Single-access enables error prevention and error protection. Whenever applicable, implement a single option for each function. Select the option according to the expected usage rate.

  Provide single-access to functions in the following conditions:

• The function is not required in emergency
• The station is highly function
• The station is intended to operate by skilled operators, who can learn and remember the access to the function.

  Provide multi-access to functions in the following conditions:

• There is a need to enable fast access to the function, such as in emergency
• The station is simple, so that there are not many chances to activate a function by mistake
• The station needs to be accessed by occasional operators, who may be used to operate other system, with different kinds of access

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Updated on 20 Apr 2016.