Heading out of UC Davis and into the experimental psychology program at San Jose State, I had the great pleasure of working at NASA Ames in the Human Factors Research Group. I could not imagine at the time that co-authoring the development of a rating scale, NASA-Task Load Index, with Dr Sandra Hart would result in being part of an internationally utilized tool, and that 25 years later would be considered one of the best in the field and still growing in use.
NASA-TLX is a subjective workload assessment tool. It allows users to perform subjective workload assessments on operator(s) working with various human-machine systems. NASA-TLX is a multi-dimensional rating procedure that derives an overall workload score based on a weighted average of ratings on six subscales.
These subscales include Mental Demands, Physical Demands, Temporal Demands, Own Performance, Effort and Frustration. It can be used to assess workload in various human-machine environments such as aircraft cockpits, command, control, and communication (C3) workstations; supervisory and process control environments; simulations and laboratory tests.
To quote Sandra Hart from a recent review - "After nearly 20 years of use, NASA-TLX has achieved a certain venerability; it is being used as a benchmark against which the efficacy of other measures, theories, or models are judged. It is described in college text books, taught in university courses, and recommended for use in situations as diverse as aircraft certification, operating rooms, nuclear power plant control rooms, simulated combat, and website design. On the other hand, the continuing series of evaluations, modifications, extensions, and applications to new situations seem to be keeping it young."
More information can be found at the NASA TLX web site -