Fit the User

Controls must be designed and located within the reach, strength, and coordination capabilities of the users. In the Introduction Module, anthropometric and biomechanic principles were introduced. Controls are an excellent example of how this knowledge is put to use.

• Reach - Reach to a control should be based on the shortest reach anticipated in the worker population, typically the reach capabilities of the 5th percentile female. The data point used should be for "functional reach." Functional reach is not just the farthest point that can be touched, but takes into consideration the need for hand use for control activation.
• Strength - The strength required for control activation should be no more than can be applied by the 5th percentile female.
• Body Size - In constrained spaces, access to controls should be based on the body dimensions of the largest worker. Typically, clearance space for each affected body dimension should be that of the 95th percentile male. If it is possible that workers could become entrapped because of size, then the 99th percentile measurements should be used.
• Coordination - The coordination required for control and display use should not exceed that which can be anticipated in the worker population.
  
  

  Placement of controls and the strength required for use must fit the worker.*

* Photos from "Behavior Based Safety and Human Factors Process at ExxonMobil," presented by Edward Hojnacki, Joint EFCOG/DOE, Chemical Management 2003 Workshop.