The performance of direct workers has a significant impact on the competitiveness of many manufacturing systems. Unfortunately, system designers are ill equipped to assess this impact during the design process. An opportunity exists to assist designers by expanding the capabilities of popular simulation modelling tools, and using them as a vehicle to better consider human factors during the process of system design manufacture. To support this requirement, this paper reports on an extensive review of literature that develops a theoretical framework, which summarizes the principal factors and relationships that such a modelling tool should incorporate.

This paper is part of a wider project to extend the scope of Discrete Event Simulation (DES) of manufacturing systems, by developing tools which can take into account the impact on system performance of direct workers (Human Performance Modelling, or HPM). In order to develop such tools, it is first necessary to demonstrate the existence of variability in worker performance, and define its magnitude, profile and impact on the overall system. The paper describes a three month empirical study which was carried out on an assembly line. Movements of components through a number of operations on the line were monitored, and additional contextual data were collected concurrently. The results of the study show that the performance of direct workers varies considerably. This finding has implications for the effectiveness of both DES and work study, and indicates the importance of the development of Human Performance Modelling tools and methods.

Discrete Event Simulation of manufacturing systems has become widely accepted as an important tool to aid the design of such systems. Often, however, it is applied by practitioners in a manner which largely ignores an important element of industry; namely, the workforce. Workers are usually represented as simple resources, often with deterministic performance values. This approach ignores the potentially large effect that human performance variation can have on a system. A long-term data collection exercise is described with the aim of quantifying the performance variation of workers in a typical automotive assembly plant. The data are presented in a histogram form which is immediately usable in simulations to improve the accuracy of design assessment. The results show levels of skewness and range which are far larger than anticipated by current researchers and practitioners in the field.

This paper is part of a wider project investigating the factors which affect the performance of workers on a production line. It describes the development of a theoretical framework for the investigation of the impact of the organisational environment on the performance of individual workers, and the experimental design for a pilot study. The improved understanding derived from the findings will ultimately be used to extend the scope of simulation models to produce more realistic predictions of worker, and hence organisational, performance.

Environmental problems, and human attempts to manage them, can be conceptualised as evolutionary complex systems, involving interlinked processes of physical, knowledge, technological, institutional, perceptual and behavioural change. A distinction may be made between changes in physical systems (`physical emergence'), changes in human knowledge about those systems (`knowledge emergence') and changes in human perceptions (`perceptual emergence'). While processes of physical and knowledge emergence are important, it is through perceptual emergence that a phenomenon comes to be regarded as a `problem' or `issue', potentially leading to changes in policy, institutional arrangements or behaviour. The paper proposes a soft complex systems model of the relationships between these processes, illustrated with examples from the history of air quality management in the UK. The model also has wider application in the understanding of other complex issues of environmental management.

The management of air pollution has a lone and complicated history in the UK. Over the centuries, the issues of concern have changed, as policy-makers have struggled to deal with the often contradictory needs of human health and life-styles within a context dictated by pre-existing conditions and institutions. As old problems are "solved", nerv ones emerge to replace them, resulting in legislation which must constantly react to unforeseen problems after they have become damaging.Within the context of modern air quality management, the behaviour causing the pollution has shifted from one directed at economic gain in limited locations - manufacturing industry - to one aimed at increasing flexibility in individual life-styles through the use of ever cheaper and more available private transport. Recent policy for managing road transport derived air pollution however, still relies on the tried and tested approach of locally oriented economic incentives based on the promotion of methods originally developed in the Alkali Acts of the nineteenth century and the Clean Air Acts of the 1950s.Using data from research into perceived utility derived from the use and ownership of the motorcar, the paper shows how the management systems for controlling pollution have now diverged from the social systems responsible for generating it. The paper concludes by suggesting the need for an approach to legislation that shifts the emphasis from the present sector-led reactive management to a more flexible and proactive approach capable of responding to issues as and when they occur.

Environmental effects such as the impact of traffic pollution on human health are subtly complex, emergent problems, which cannot be managed adequately within existing analytical approaches and institutiona frameworks. Using a case study of transport related tropospheric ozone management in the South Central region of the United Kingdom, this paper demonstrates that the management of complex regional problems requires both a thorough understanding of the natural processes involved, and a recognition of differences in perception and institutional responsibilities at different geographical scales.