Conditions for maintaining ageing operators at work—a case study conducted at an automobile manufacturing plant

Applied Ergonomics 31 (2000) 453}462

Conditions for maintaining ageing operators at work*a case study conducted at an automobile manufacturing plant Corinne Gaudart* CREAPT, 41, rue Gay Lussac, 75005 Paris, France Received 28 September 1998; accepted 14 March 2000

Abstract This is a case study on work/ageing relations in an automobile manufacturing company, where demographic trends and the work organisation determine the conditions under which ageing operators can work in repetitive tasks under tight time constraints. The methodology used is based on a comparison of di!erent age operators at their regular workstation and in a new job, during the training process. The older workers appear to develop health-preserving strategies of work while achieving production goals. The possibility of setting up such strategies depends on the job characteristics. More generally, this case study allows us to better understand why some older workers are excluded from certain workstations, and thus why `polyvalencya or job rotation decreases with age.  2000 Elsevier Science Ltd. All rights reserved. Keywords: Ageing; Repetitive tasks; Experience

1. Introduction It is necessary to understand the complexity of relations between ageing and work to better adapt work situations to the characteristics of ageing populations. This objective should be seen in a particular social and economic context in France. Retirement age ranges from 60 to 65 but this can be moderated by early retirement policies, partially "nanced by State plans, to maintain a balance in jobs. Enterprises may choose to do so to increase productivity or to adapt employees to conditions of work. Until the late 1980s, the ageing of the working population was masked by early retirement measures, in particular when work constraints were critical for ageing workers, for instance severe and tight time pressures, night shifts, demanding e!orts or strenuous postures , whose e!ects on health are well known (Volko! et al., 1996). At present the process of exclusion or protection of older workers is less systematic and occurs at a later age, the employment crisis prevents companies from hiring young people and State authorities are reduc-

* Corresponding author. Tel.: -33-01-44-10}78-93; fax: 33-01-44-4171-69. E-mail address: [email protected] (C. Gaudart).

ing the measures to support early retirement. Together with the general demographic trends, this means that the proportion of ageing workers is rising (MolinieH , 1998). Moreover, the reinforcement of strategies to rationalise work and its organisation prevents any reduction in the number of workers subjected to strenuous constraints (CeH zard et al., 1991) and maintains ageing workers in situations in which these constraints persist. Our investigation was conducted within the above context in an automobile manufacturing company, whose policy is to keep older workers on the assembly line (Laville et al., 1997). The project aimed to adjust work situations to the ageing population's characteristics and stems from the concerns this company put forward to the resembles at CREAPT: work requirements on assembly lines have changed; in particular the need for `polyvalencya faces ageing operators with di$culties as soon as they turn 40 yr old.

 We de"ne `polyvalencya or job rotation as the number of workstations that operators occupy. We de"ne a workstation as a set of tasks and means assigned to the operator. Several operators on the same workstation must therefore carry out the same tasks using the same means.

0003-6870/00/$ - see front matter  2000 Elsevier Science Ltd. All rights reserved. PII: S 0 0 0 3 - 6 8 7 0 ( 0 0 ) 0 0 0 2 4 - 7

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2. General principles of methodology Studying the relations between ageing and work is a complex issue because they are pluridimensional, and involve ageing both `on account of worka and also `with regard to worka (Teiger, 1989). To understand these relations, at least two levels must be considered: E an individual level referring to the changes with age in physiological and cognitive abilities to carry out a speci"c task; E a collective level encompassing the individual changes with age in the broader framework of a changing work environment; technological and organisational developments in turn have an impact on individual ageing (Laville and Volko!, 1996). To analyse the relations between ageing and work the methodology applied must include this pluridimensionality (Gaudart, 1996a, b). The study was conducted at one of the automobile production plants and the methodology followed in this case study could be described as a `funnel-typea approach: based on general quantitative data pertaining to a large population, the focus is gradually centred on a detailed qualitative analysis of a few operators at the industrial workplace. The status of the data collected di!ers: the former data enable a description of work and the population concerned whereas the latter explain the relations between ageing and work. The study comprised three stages: E Stage 1: in view of understanding the nature of new work requirements we gathered data on the company's demographic, economic and technological context, drawn from national surveys on working conditions, company documentation and sta! interviews in di!erent departments of the plant; E Stage 2: we then proceeded to analyse the change in `polyvalencya requirements with age in each department of the plant; E Stage 3: we "nally compared the operational modes and strategies applied by young and older operators in two situations: E 䡩 one in which the operators are familiar with the workstation; E 䡩 one in which the operators are in the process of training on a new workstation.

work under rigid time constraints similar to that observed on the production lines of this plant is increasing in pravelence. In 1991, 1.6 million employees (i.e. 8.5% of the total number) 1.3 million of whom are blue collar workers (i.e. 20.2% of blue collar workers) stated, in a national survey questionnaire on working conditions, that they either worked on an assembly line or their work pace was imposed by the automatic movements of a product or the automatic pace of a machine; in 1984, it was the case for 6.8% total employees and 16.8% blue collar workers. This progression can be explained by two factors: the number of workstations with tight constraints is either the same or has increased and certain `softa jobs such as maintenance or preparation are decreasing. No age category is spared any longer by this type of work organisation (Fig. 1). The operators who are over 40 years old are increasingly faced with assembly line work (Gaudart et al., 1995). Moreover, it is known that when time contraints are too tight they lead to the exclusion of workers over 40 from the company due to their decrease in productivity and inability to keep up with the pace of work (Teiger, 1998). For a long time selection mechanisms would gradually shift ageing workers away from these types of work constraints (Volko! and MolinieH , 1998): this was rather a selection/exclusion in sectors with high labour turnovers and a young work population (garment industry) and more of a selection/reassignment to the so-called `softa jobs in sectors where the labour turnover was lower such as in automobile manufacturing. These selection modes are now challenged in the automobile industry because workers there remain in the company and outsourcing policies make their reassignment o! the assembly line impossible; this means an increasing number of ageing workers must be reassigned, when there are less and less possibilities of reemployment.

3. Review of ageing problems in the French automobile industry 3.1. Persistence of assembly line work The 1984 and 1991 national survey questionnaires on working conditions show that the type of assembly line

Fig. 1. Age distribution of assembly line workers from 1984 to 1991 for automobile industry workers in France. Note: Sources: Ministry of Labour ,National surveys on working conditions (1984, 1991).

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3.2. The population is concentrated in certain age groups General demographic trends, sta! cuts in the automobile manufacturing industry (MolinieH , 1998) and measures favouring early retirement have tightened up the age structures in companies, leading to an increase in the intermediary age groups. In 1994, at the plant under investigation, 65% of the employees were 35}49 years old. Whatever the assumptions for the incoming and outgoing workers and unless a large number of young people are hired, this plant as well as the whole company is bound to age in the years to come. 3.3. An increasing demand for yexibility The economic crisis and the development of competition have led the company to gradually change the organisation of its production: E sta! cuts have led the company to stress the need for #exibility among operators: developing `polyvalencya therefore becomes crucial and, in peak work-load periods, the company employs young temporary workers; E competition has also led to the need for #exibility in production: with a wide range of versions and options of the same vehicle, a variety of work procedures at workstations, standardisation of production lines based on a 1 min average cycle time, and the introduction of just-in-time production, work has become increasingly complex. Henceforth, operators have to be familiar with several increasingly complex workstations. The following conclusions can thus be drawn from this preliminary information: E There is less possibility to reassign the ageing sta!: the development of outsourcing as well as just-in-time forms of production do away with o!-the-line jobs, preparation jobs that are less subject to time constraints and were often a solution to the problem of reassigning ageing sta!. E Temporary workers: more operating #exibility for production lines 2 greater instability. Because of the age structures, temporary workers represent the young labour force ()25 years) who accomplish the more physically demanding jobs, given the di$culties of the older workers. At periods with heavy work loads, temporary workers can represent up to 50% of the sta!. Conversely, when work loads are below average, they disappear causing the older operators to do jobs that are di$cult for them. E A greater #exibility is required of older operators: because of a tightly sized sta! and the instability of the young labour force the need for `polyvalencya is greater among the full-time employees, that is the ageing workers.

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This "rst analysis therefore enables us to reposition the problem. The di$culties of the older workers to remain on these types of jobs may not only be due to a decrease in individual physiological and cognitive abilities, but also to organisational and technological changes in work which exacerbated their di$culties, as well as a demographic trend making it harder to reassign them.

4. The change of `polyvalencya with age in the plant 4.1. Method Each team leader noted the operators assigned to a workstation for each shift on a rotation schedule, over a 4-week period. We then conducted a statistical analysis including the operators' ages. The study covered 734 operators in the "nal assembly department, and paint and steel sheet shops. 4.2. Results The proportion of workers maintaining one single job for no less than 4 weeks is always greater among the older workers (Table 1). But there are di!erences from one department to another, or one workshop to another. The decrease in `polyvalencya with age is sharper in the mechanics and mouldings shop ("nal assembling department); but these assembly lines are also the most constrained with a constant #ow of products and few possibilities for bu!er stocks. In the paint shop work pace is determined by machine cycles (painting robots) and in the steel sheet shop the product stops at the workstation just in front of the operator who releases it later.

4.3. Discussion `Polyvalencya is decreasing with age at a time when the company needs more #exibility (MolinieH et al., 1996). The explanation most often suggested is based on a decrease in motivation with age. But there could be a generation e!ect: there are more North African workers among the older ones, who have more reading di$culties that hinder `polyvalencya. Furthermore, `polyvalencya was encouraged less in the past than it is today. Because of this generation e!ect, caution is required before extrapolating to the young worker generations 20 years from now. Nevertheless, given the work requirements, the fact that `polyvalencya decreases with age in today's ageing population remains a major problem for the company and it cannot only be attributed to demotivation. This is what will be shown by analyses of workstations comparing older and younger workers' operating modes.

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Table 1 Changes in `polyvalencya with age in the plant Mechanics

(35 35}39 40}44 45

Mouldings

Paint

Sheet rolling mill

%1 workstation

%5 workstations

%1 workstation

%5 workstations

%1 workstation

%5 workstations

%1 workstation

%5 workstations

8 23 50 74

48 23 4 3

5 41 52 55

41 21 0 3

7 21 22 41

42 33 35 22

2 6 9 10

74 60 43 46

5. The change in operating modes with age on well-known workstations 5.1. Method Decrease in `polyvalencya being most marked in the "nal assembly department, a workstation in the mechanics shop and one in the mouldings shop were chosen in this department (Table 1) to compare operating modes at di!erent ages. Both workstations were selected on the basis of two criteria (Tables 2 and 3): E each workstation had to be operated by several workers during both shifts (2;8 h); E there had to be a broad range of ages. Because it was hard to ful"l both criteria, seniority at the workstation could not be taken into account: it appears in Tables 2 and 3 for information. The observation method to study these operators consisted in "lming them during some 20 work cycles (at the time the theoretical cycle time was 90 s). These observations were carefully examined to highlight the time and sequence of operations for each cycle. Then each operation was classi"ed according to the following work categories or stages: collecting information to identify the model and choose the parts to assemble; picking the parts to assemble; assembling, including pre-screwing (hand-screwing) and screwing with an air-compression tool; going back and forth to pick up the parts. These activity analyses were supplemented by interviews with both the operators observed and the others, in both of the units where observations were made, in order to validate the results. 5.2. Results in the mechanics shop Two results that we consider to be the most characteristic one can be derived from the analysis of cycle times and work stages in the mechanics shop. The theoretical cycle time (90 s) is obviously imposed on all operators regardless of their age. The time di!erences observed from one operator to another re#ect the

Table 2 Age and seniority of operators studies in mechanics Operator code

Seniority at workstation

Op30a Op30b Op38 Op45 Op46

2 months 3 days 1 year 6 months 4 years

Op30, operator age 30.

Table 3 Age and seniority of operators studied in mouldings Operator code

Seniority at workstation

Op22 Op23 Op42 Op47 Op54

2 weeks 3 weeks 3 days 6 years 4 years

characteristics of the observation period (with a proportion of more `di$culta models than others during this period) more than actual di!erences in operator `performancesa. On the other hand, the marked variations in time are mostly noted among young operators (Table 4). More than their elders, these younger workers can alternate `relaxinga stages with acceleration periods allowing them to catch up and even get ahead of the line. The interviews with all the operators con"rm this hypothesis: the older ones say they do not try to move up the line (get ahead of their workstation) and are less prone than the younger ones to cooperate with the colleagues closest to them. This statement, together with the result showing a decrease in job rotation with age, may be interpreted as the fact that older operators choose to protect themselves in a work environment as far as possible from any disturbance. The analysis of back and forth movements phases (Table 5) shows that the average time here is shorter for

C. Gaudart / Applied Ergonomics 31 (2000) 453}462 Table 4 Analysis of work cycle times at the mechanics workstation

Table 5 Analysis of time spent on back and forth movements per work cycle for each work cycle at the mechanics workstation

Time (s)

Op30a

Op30b Op38

Op45

Op46

Average time Maximum time Minimum time Variation (max. time!min. time)

94 147 58 89

98 146 81 65

84 101 68 33

82 109 68 41

91 124 75 49

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Op45 and Op46; this result is less noticeable for Op38. Here again marked variations in time occur mostly among the younger operators. By analysing these times it is possible to perceive the di!erences between young operators and older ones, but this type of merely quantitative analysis fails to explain the dynamics of the operators' activity. Hence our interest in the distribution of the work stages, and in particular the stage where they are walking around (back and forth movements) and the one where they are picking parts to assemble, related to such movements. Clear di!erences in strategy can be noted according to age. An illustration of this is the way a young operator, Op30a, and an older one, Op46, distribute their back and forth movements and stocking actions at the same workstation which are typical of the operator group they belong to (Figs. 2 and 3).

Time (s)

Op30a Op30b Op38

Op45

Op46

Average time Maximum time Minimum time Variation (max. time!min. time)

12 34 6 28

7 16 2 14

8 14 5 9

16 55 7 48

14 21 9 12

The older workers clearly concentrate supply operations at the beginning of the work cycle and renew supplies once or twice a little later, without having to move around most of the time. The video shows that, as the line is in constant motion, these operator s manage to "nd themselves at the right moment in the storage areas to collect supplies. Through this "ne management of space and time they spare their movements with regard to the younger ones. The latter adopt another strategy consisting in gathering supplies and assembling parts one by one which implies moving around more often. It appears from the interviews with operators that the stocking strategy protects them as far as possible from physical strain and saves time and gives them freedom to react should an incident occur. This strategy is based on

Fig. 2. Distribution of the stocking stage and back and forth movements per cycle for Op30a.

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Fig. 3. Distribution of the stocking stage and back and forth movements per cycle for Op46.

the development of "ne skills: the operators pick up to 7 screws or bolts in their right hand to stock them in their left hand, each one in a speci"c place. When they start assembling, they shift each one of them from their palm or their "nger to their left-hand "ngertips so that their right hand can pick them and screw them on the part, without them having to look and check. Another example shows that the screwing operation is checked by tactile, feedback rather than by sight, which means operators do not have to bend over.

Table 6 Analysis of cycle times at the mouldings workstations Time (s)

Op22

Op23

Op42

Op47

Op54

Average time Maximum time Minimum time Variation (max. time!min. time)

150 182 125 57

128 173 70 103

156 178 140 38

118 137 88 49

139 164 124 40

5.3. Results in the mouldings shop At this workstation, a quantitative analysis of work stage times does not yield the same results. There is still a di!erence, though not as marked as in the mechanics shop, between ages in the variations of cycle times (Table 6). Furthermore, the time-saving and journey-sparing strategies described earlier do not appear at this workstation. On the contrary, the older ones spend more time than the younger ones checking the data sheet to choose the right parts to assemble (between several possible types of parts) on the di!erent models (Table 7). Here the younger ones group the supplies together and manage the space around the workstation whereas the older ones pick up one part at a time. During the interviews, the younger operators claim that this workstation is an easy one whereas the older ones regard it as di$cult because of the di!erent types of

Table 7 Analysis of cycle times at the mouldings work stations Time (s)

Op22

Op23

Op42

Op47

Op54

Average time Maximum time Minimum time Variation (max. time!min. time)

5 7 3 5

4 9 0 9

5 8 2 6

8 14 0 14

14 20 10 10

parts and the number of possible combinations. To avoid errors or omissions the older ones take a glance at the data sheet each time they pick up supplies and even at the end of cycles to check; this prevents them from grouping their stocks and thus from sparing e!ort and saving time.

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5.4. Discussion The analyses reveal two important objectives perceived by the older operators: E ensuring production in a given time while meeting high-quality standards; E reducing physical activity to preserve their health. Depending on the requirements imposed by the work situation, these two concerns may be compatible or con#icting. In the latter case, it will be up to the operator to prontise one of the objectives over the other. The importance of both these concerns varies from one operator to another, age being a determining factor. The strategies set up by the older operators at the mechanics workstation seem to respond to the following concerns: avoid unnecessary e!orts which implies developing knacks and "ne skills, and seeking regularity in performance times that are closely related to the workstation characteristics. In the mouldings shop, the demands are greater: there are many di!erent models and therefore di!erent assembling operations, physical e!orts are great because of the weight of the objects to be carried and the number of journeys back and forth. The older ones will thus elaborate strategies to avoid errors or omissions which leaves little freedom to do things di!erently; the quality of production is the most important issue. The analysis of these two workstations clearly illustrates where the di!erences in operating modes lie according to the age of operators, and the reason for such di!erences. It also shows how dependent these operating modes are on the job characteristics and how fragile the balance remains. Strategies associating `health and qualitya issues cannot be elaborated for every single workstation; and those elaborated for one workstation cannot always be transferred to another without adjustments. The success of such adjustments and their cost are still di$cult to predict for these operators. This would seem to corroborate that `polyvalencya decreases with age. The question now is how these strategies are developed, whether they are set up during training periods and what di$culties during these periods may explain why `polyvalencya decreases with age.

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545 work cycles were studied during the 11 training sessions in the mechanics and mouldings shops. In this study trainees are divided into two groups: a `younga group including operators from age 19 to 30 (n"6) and an older group including operators from age 36 to 53 (n"5). Training sessions were observed entirely or partially depending on the production constraints and the number of sta!. The data were collected on and o!, according to the events arising during the training sessions. Several observation variables were chosen: the operating modes of both tutors and trainees; incidents (di$culties in handling, dropping of parts, omissions, ...); and communications. Tutors and trainees were also questioned on the training di$culties. The data collected were then processed in the form of statistics on age and training periods, and in a more qualitative manner to highlight the acquisition of operation sequences and skills. Some of the results yielded by the statistical study will be elaborated below. 6.2. Results The younger trainees manage to achieve the total number of operations in a work cycle at an earlier stage (Fig. 4). The percentage of cycles in which all the operations are performed rises according to the time spent on training, for all operators; this is because the general acquisition of the job is done by gradually adding one operation on to the next. There are, however, di!erences between the younger and the older operators. After a few hours' training, the proportion of cycles entirely performed by the younger workers is greater than for the older ones. Older operators appear to set up strategies to preserve their health (Fig. 5). Fig. 5, encompassing 4 jobs (two operators per group), shows a distinction from the point of view of age in the "rst few hours of training: the older ones use the stocking strategy (see stocking stages for Op45 and Op46) much more than the younger ones since the very "rst hours. This strategy, with the implications studied earlier*it avoids too many journeys back and forth and aims at preserving ageing operators health*is thus implemented by older operators from the very start of their learning process. 6.3. Discussion

6. The change in training with age at workstations that operators are unfamiliar with 6.1. Method These observations were made in the "nal assembly department (mechanics and mouldings). The workstation operator becomes the instructor for training purposes. The training time in theory is not pre-de"ned, though training usually lasts for a few days.

An analysis of the di!erent training modes according to age shows that young workers complete fairly soon a greater number of cycles than their elders. This di!erence is not due to particular di$culties experienced by the older operators. To achieve the same result they use di!erent strategies as soon as they start training: they try out assembling each part before doing all the operations which means that they are cautious in the acquisition of speed; they pick up supplies together as

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Fig. 4. Percentage of cycles completed by trainees according to age and the length of the training period.

Fig. 5. Percentage of cycles using the `pickinga strategy at least once. as a function of age and the length of the training period. Note: In the older group, observations for the two training periods concerned with the use of this strategy ended before the 16th hour, either because their training was completed or because it was not possible to study them beyond that period.

much as possible when their job permits, which means less moving around. These strategies are intended to give them more leeway so they are less subject to assembly line constraints: time constraints and a variety of di!erent assembling operations on vehicles that come in randomly. The younger ones also use such strategies, though not as systematically. The purpose and meaning of training is therefore not the same for both age groups. 7. General discussion In our view, this case study leads to two di!erent types of results: E at the plant level, the study allows better understanding of why `polyvalencya decreases with age. It goes

beyond the usual explanation given, that is: motivation decreases with age and older workers cannot face new situations. E more generally, it adds a further dimension to the conditions required to maintain ageing operators at their workstation without a!ecting health and production. The decrease in `polyvalencya with age could be a sign that older workers fail to train for another job and cannot deal with a di!erent workstation in a di$cult context: training conditions do not provide for the necessary stability to learn; often `improviseda job rotations require adjusting very fast to a new work situation; "nally, because the heads of departments cannot plan training without a risk of error, they often select the

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younger operators. But this decrease in `polyvalencya with age can also be interpreted as yet another healthpreserving strategy applied by older workers: maintaining skills in a single job could be a means of guarding themselves from the strain caused by changing jobs. Decrease in `polyvalencya can result either from the strategy implemented by the team leader or the operators themselves. It can be explained by: E on the one hand, the uncertainty of the senior workers as to the di$culties of their new job and their ability to overcome them, and in particular whether they can transfer the strategies they may have already developed, depending on the job characteristics; E on the other hand, they could experience di$culties inherent in the learning period itself as to whether or not it is possible to implement their own strategies. A study on the acquisition of new jobs has attempted to elicit this. The generalisation of these results faces problems that are well known in ergonomics: is it possible to transfer the results of a case study covering a small number of operators to other production situations? Though the data used here were collected at the "nal assembling department, it should be stressed that the conditions for them to be `representativea are not met. The working or training situations are extremely variable and unpredictable as the data are collected in real work situations. Because of that it is not possible to elaborate a rigorous observation plan based on a random sampling or in which the main variation factors could be controlled `a prioria. Under such circumstances, the question of signi"cance is left pending because of the limited number of operators for whom systematic data were collected, and because signi"cance tests are not supposed to be applied to these statistical units that are not drawn randomly. To the usual di$culties brought about by a crosssectional approach must be added those arising from the observation of real work situations. It was not possible to make rigorous comparisons relating the di!erences between the age groups to seniority or experience, as it was not possible to choose the characteristics either for the population studied or for the past or present jobs. The interpretation bias that could have resulted from this situation led us to seek other ways of validating our "ndings. Though the single results may have no demonstration value, their validity derives from their consistency and acceptance by the operators concerned at the time they were restored. We therefore believe that this way of validating contributes to on-going discussions in enterprises on the terms in which ageing operators can be maintained. This case study brings out the importance of the older workers' experience: where the work conditions are favourable, the work strategies derived from experience are

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a factor in maintaining the ageing operators at their workstation. This study also allows a more thorough de"nation of the nature of this experience. Three ideas can be set forth: E Firstly, the older workers' experience does not particularly involve skills relating to assembling techniques*given the fact that tasks are repetitive, young workers have them as well*but rather to organisational skills, linked with a tight management of space and time. The skills are not speci"c to jobs but rather to types of tasks. But the job characteristics and workplace layout will determine the development of such skills. E Secondly, the experience of senior operators is di!erent from the younger ones because it develops on the basis of declining physical and cognitive capabilities or valuerability or a fragilisation because of an accumulation of certain work constraints. Knowledge and awareness of one's limits in this context leave them to avoid work situations that are damaging for their health; therefore it stems from health and health protection concerns. E Thirdly, this experience is made up both of rigidity and plasticity; the results show that older workers are capable of setting up particular strategies but implementing them requires a su$ciently stable environment and/or a well-controlled job. Thus we do not believe that the phenomena linked to declining capacities and ageing are separate from those derived from experience (Welford, 1958; Salthouse, 1990). Because operators are aware of these inexorable declining processes, they use them to their advantage to build their experience: experience is thus a combination of decline and development (Fig. 6).

Fig. 6. Relations between ageing, work and experience.

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Whether this experience can be used at work depends on the job requirements and the work organisation. Making use of this experience may in turn have implications for health, by softening its deterioration (through compensatory mechanisms*Salthouse, 1990), and on the development of skills by enriching the operators' experience. In this context, actions should be taken to preserve the older operators' health while developing their skills (Laville, 1998). This means re#ecting on the way to encourage the use of this experience and adapt workstations. But according to the results of our investigation, this dimension would not be su$cient. Actions must also encompass organisation of work, management of sta! and training, including reconsidering at every rank in the hierarchy and for each function in the company for inter-individual variability. In their own way, ageing operators apply strategies re#ecting organisational skills and implying a particular combination of #exibility and rigidity. Such strategies give clues as to how to determine how much leeway operators have to organise their work in a context marked by an increasing diversity of products and tighter time constraints.

References CeH zard, M., Dussert, F., Gollac, M., 1991. Les changements dans l'organisation du travail. Premie`res Informations Vol. 253. Gaudart, C., 1996a. Transformations de l'activiteH avec l'a( ge dans des ta( ches de montage automobile sur cham( ne. EPHE, Laboratoire d'Ergonomie Physiologique et Cognitive. Ph.D. in Ergonomics.

Gaudart, C., 1996b. Ageing and learning after 40 in an automobile assembly line. Proceedings from a Scienti"c Conference, Work after 45? Stockholm, Sweden, Vol. 1, pp. 100}105. Gaudart, C., Laville, A., MolinieH , A.F., Volko!, S., 1995. Age des opeH rateurs et travail reH peH titif } Une approche deH mographique et ergonomique. Relations Industrielles (Montreal) 50 (4), 826}851. Laville, A., 1998. Work and ages, from research to action. In: MarquieH , J.C., Paume`s, D., Volko!, S. (Eds.), Working with Age. Taylor & Francis, London, pp. 569}582. Laville, A., Sailly, M., Volko!, S., 1997. Age and work on assembly lines: studies and actions in an automobile construction plant. Proceedings of the 13th Congress of IEA, Tampere, Finland, Vol. 5, pp. 53}65. Laville, A., Volko!, S., 1996. Age-work relationships: elaboration of multidisciplinary approach. Book of abstract from a Scienti"c Conference, Work after 45?, Stockholm, Sweden, pp. 74}75. MolinieH , A.F., 1998. The `ageinga of the Workforce. In: MarquieH , J.C., Paume`s, D., Volko!, S. (Eds.), Working with Age. Taylor & Francis, London, pp. 103}125. MolinieH , A.F., Volko!, S., Gaudart, C., 1996. Occuper plusieurs postes de travail devient plus rare avec l'a( ge: approches quantitatives et eH leH ments d'interpreH tation. In: Patesson, R. (Ed.), Intervenir par l'ergonomie, Proceedings of the XXXIth Congress of SELF, Bruxelles, Belgium, Vol. 2, pp. 47}53. Salthouse, T.A., 1990. In#uence of experience on age di!erences in cognitive functioning. Human Factors 32 (5), 551}569. Teiger, C., 1989. Le vieillissement di!eH rentiel dans et par le travail, un vieux proble`me dans un contexte reH cent. Le Travail Humain 52 (1), 21}56. Teiger, C., 1998. Ways of thinking out the age work relationship in the course of time. In: MarquieH , J.C., Paume`s, D., Volko!, S. (Eds.), Working with Age. Taylor & Francis, London, pp. 18}97. Volko!, S., MolinieH , A.F., Davezies, P., 1996. Selection e!ects, di!ered e!ects, interaction e!ects: some results of quantitative investigations on age-work-health relationships? Proceedings from a Scienti"c Conference, Work after 45? Stockholm, Sweden, Vol. 2, pp. 293}299. Volko!, S., MolinieH , A.F., 1998. Elements for a demography of work. In: MarquieH , J.C., Paume`s, D., Volko!, S. (Eds.), Working with Age. Taylor & Francis, London, pp. 126}160. Welford, A.T., 1958. Ageing and Human Skill. Oxford University Press, London.