Predetermined motion time systems (PMTS)

Predetermined motion time systems (PMTS) are work measurement systems based on the analysis of work into basic human movements, classified according to the nature of each movement and the conditions under which it is made. Tables of data provide a time, at a defined rate of working, for each classification of each movement.

The first PMTS (since designated as "first-level" systems) were designed to provide times for detailed manual work and thus consisted of fundamental movements (reach, grasp, move, etc) and associated times.

Large amounts of research, data collection, analysis, synthesis, and validation are required to produce PMTS data and the number of such systems is very low. "Higher level" systems have since been devised, most commonly by combining these fundamental movements into common, simple manual tasks. Such higher level systems are designed for faster standard setting of longer cycle activity.

Criticisms of PMTS relate to their inability to provide data for movements made under "unnatural" conditions (such as working in cramped conditions or with an unnatural body posture) or for mental processes and their difficulty in coping with work which is subject to interruptions. However, various systems have been derived for "office work," which include tasks with a simple and predictable mental content.

Conversely, one of the significant advantages of PMTS is that they require a detailed description of the working method - and are thus useful for studying how work is done (and how it can be improved) as well as measuring the time it should take.

Many PMTS are proprietary systems and users must either attend a designated and approved training course and/or pay a royalty for use of the data.

One of the major PMTS systems is MTM (Methods-Times Measurement) which is actually a 'family' of systems operating at different levels and and applicable to different types of work. MTM1 - the 'highest-level' or most detailed member of the family - was developed in the 1940s by analysing large numbers of repetitive cycles of manual work on film. MTM gives values for such basic hand/arm motions as : Reach, Move, Turn, Grasp, Position, Disengage, and Release, together with a small set of full body motions. The time taken to Reach to an object is then given by a table based on the kind of Reach (e.g. whether the object is in a fixed location - such as a tool in a tool holder - or is a single object located on a bench, or jumbled together with other objects, etc.) and the distance to be Reached. Similar tables give times for each of the other basic movements categorised and measured similarly. MTM is suitable for measuring short cycle, highly-repetitive work. Other members of the MTM family use lower level motions (so that in MTM2, for example, the MTM1 motions of Reach and Grasp are combined into a composite motion, GET). MTM2 is thus quicker to apply, but more suited to longer-cycle work where the fine level of discrimination of MTM1 is unnecessary in terms of meeting accuracy requirements.