Figure 4: Clearing a blockage link analysis after redesign Machine 1 Machine 2 Machine 3 Machine 4 Machine 5 Isolation Point Operator Time-line Analysis There are many different ergonomics methods which consider the timing of tasks and operations in the workplace. Many of these are designed to increase the efficiency of the process, to identify staffing needs or to predict how much product an individual or team can process e.g. time and motion studies. Timeline analysis is described here because it is an appropriate method for understanding the demands placed on an operator by their role. Full timeline analysis is a complex method which requires a knowledge of human information processing, and companies should seek competent advice before applying it. However, simply mapping activities against a timeline can be informative. 4
Timeline analysis can be used proactively to identify tasks or combinations of tasks which place too much demand in an individual’s ability to process information. A drawback to using anytime study such as this one is that it can be hard to predict the demands placed on an operative by abnormal events such as plant upsets in the process industry. Timeline analysis can also be used reactively (as in the example given in figure 5 below) to illuminate why an operative may have failed to complete a task successfully. As with the other task analysis methods described here, timeline analysis is based on task observations and walk / talk throughs. In addition, timings are taken of either individual task steps or tasks (as in the example below) as appropriate. These are then mapped against a timeline to see which activities take place simultaneously. In order to understand the demands simultaneous tasks place on a person, human factors specialists refer to the sensory and output modalities the task takes place in. For example, when we are speaking to someone, the sensory modality is auditory and the output modality is verbal. When we are driving a car, the sensory modality is visuo- spatial and the output modality is manual. Human beings have a limited information processing resource. When demands are light, people are able to speak to someone and drive a carat the same time. However, should demands increase (a distressing conversation, a complex driving environment, the demands placed on the information processing resource mean that performance will deteriorate on one task or the other.