Fitts List

In BS/EN/ISO 11064-1 2001 preliminary function allocations are performed using an overview approach comprised of four basic heuristics. Human factors best practice offers an extension to this approach in the form of Fitts List (Fitts, 1951). The expanded collection of heuristics is anchored around information-processing stages and the relative performance of humans or automation in performing them. Fitts List is shown in Table 7.4. 

Nevertheless, heuristics remain an established part of the relevant standards and an accepted, expedient approach. The limitations inherent in them are overcome to some extent by embedding them within an iterative design cycle, such that 

FIGURE 7.7 Flowchart illustrating the process of applying Marsden and Kirby s (2005) allocation of fnnction analysis. 

Fitts List Provides Additional Heuristics for Preliminary Function 

Information acquisition Detecting small and meaningful amounts of change Detecting a wide range of stimuli 

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On what basis should this task allocation be decided The most obvious way to separate functions, given that constraints such as cost-benefit have been considered, is on the relative capabilities and limitations of the two components. Such an approach was attempted by Fitts in drawing up his now famous list itemising the relative advantages of men and machines. An updated version of the so-called Fitts List as modified by Singleton is shown in Table 23.1. 

Part III Occupational health and hygiene Table 23.1. An updated version of the Fitts List (from Singleton )... 

The first step is to allocate the abstract operational-level Safety Functions on to the logical model at this point it is helpful to have a broad notion of how the human and machine will interact in delivering the Safety Functions. The early work of Fitts (1951) was often used to derive MABA-MABA (Men Are Better At-Machines Are Better At) lists that were typically restricted to considerations of either the human or the machine performing each individual function. However, since Fitts early work, it has become sqiparent that many functions in complex systems require sqiportionment of the function between both human and machine. 

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