MAP-01-011 HFI Technical Guide - Human Factors Integration ...

MAP-01-011 – HFI Technical Guide (STGP 11)• Using primary and secondary task performance measures may proveexpensive, as simulators and computers are required.A3.6.3Task Load Index (NASA-TLX)The NASA Task Load Index (TLX) (DTC072 - Hart and Staveland 1988) is amulti-dimensional rating tool is a subjective workload assessment tool thatworkload rating based upon a weighted average of six workload sub-scaleratings. The six sub-scales and their associated definitions are given below:1. Mental demand – How much thinking, deciding, calculating, remembering,looking, searching etc was required and was the task easy or demanding,simple or complex, exacting or forgiving?2. Physical demand – How much physical activity was required e.g. pushing,pulling, turning, controlling, activating etc. Was the task easy ordemanding, slow or brisk, slack or strenuous, restful or laborious?3. Temporal demand – How much time pressure did you feel due to the rateor pace at which the tasks or task elements occurred? Was the pace slowand leisurely or rapid and frantic?4. Effort – How hard did you have to work (Mentally and physically) toaccomplish your level of performance?5. Performance – How successful do you think you were in accomplishingthe goals of the task set by the analyst (or yourself)? How satisfied wereyou with your performance in accomplishing these goals.6. Frustration level – How insecure, discouraged, irritated, stressed andannoyed versus secure, gratified, content, relaxed and complacent did youfeel during the task?NASA-TLX is the most commonly used subjective workload assessmenttechnique and has been applied to the civil and military aviation, driving, andNuclear power plant control room operation and air traffic control domains.• Advantages• NASA TLX provides a quick and simple technique for estimating operatorworkload.• NASA TLX sub-scales are generic, so the technique can be applied to anydomain.• The NASA TLX has been tested thoroughly in the past and has also beenthe subject of a number of validation studies.• The provision of the TLX software package removes most of the work forthe analyst, resulting in a very quick and simple procedure. For thosewithout computers, the TLX is also available in a pen and paper format.• Probably the most widely used technique for estimating operator workload.May 2006 Page A3-46 Issue 4