slips , trips and falls ( stfs ) lead recurrently to injuries in occupational situations1 .
these accidents are triggered by a movement 
 disturbance ( a slip or a trip ) when working , especially when walking .
other movement 
 disturbances ( a wrench slipping , an arm colliding with a wall , etc . ) can occur in 
 occupational situations ; moreover , these can arise when performing different types of tasks 
 ( tightening a bolt , moving an item alone or with a colleague , etc . ) .
this paper considers 
 ostfs and , more broadly , occupational accidents with movement disturbance ( oamds ) ; the 
 latter composing a set of accidents operationally defined by leclercq et 
 al.2 , 3 , which involve a heavy cost in both human and financial terms4 .
the literature often advances workplace design and upkeep5 , 6 , access system 
 configuration7 or , again , human 
 factors8 , 9 for explaining ostfas . implementing actions that neutralise these 
 factors to secure displacements ,
however , such actions frequently overlook not only task diversity , but also production 
 requirements and they can therefore only offer a partial response to preventing all oamds . 

research into these accidents shows that , as in all occupational accidents , many 
 accident - causing event configurations stem from arbitration between production and safety , 
 which can not be overlooked if progress is to be achieved in the prevention field . 

production - safety arbitrations lead to controls applied under working conditions in order to 
 perform the task while maintaining safety .
the control most frequently referred to involves walking 
 fast to try to absorb a delay or confront an emergency .
these observations provide a partial 
 explanation for worker difficulties in systematically applying certain recommendations based 
 on common sense ( e.g.  do nt rush  ) that are aimed at preventing oamds .
this paper describes initially the need for , and limits involved in , neutralising the 
 environmental factors in play and subsequently the production - safety arbitrations prompted 
 by the so - called  organisational  oamd factors referred to in the 
 literature .
some of these arbitrations imply control implementation by the worker performing 
 the task , which is then reflected in his / her displacements or , more generally , in his / her 
 movements that increase exposure to oamd risk . focusing on organisational factors allows us 
 to integrate these controls into a set highlighted by a general work organisation model . 

such a model indicates areas of similarity between oamd genesis and other occupational 
 injury geneses .
movement disturbance factors may be permanent and visible ( floor in poor condition , 
 congestion , difficult access to parts of a machine , etc . ) in some work situations and may 
 expose many workers over relatively long periods .
this is the case of slippery floors in 
 food processing shops , for example .
such factors , along with  haste  ,  carelessness  and 
  awkwardness  are frequently advanced when explaining oamd occurrence .
neutralising environmental factors often involves taking action on certain working 
 conditions ( installing a slip - resistant floor , reconfiguring an access system , etc . ) .
it is 
 commonplace for companies that decide to raise their oamd - related safety level primarily 
 focus of this type of action .
however , in common with instructions designed to change 
 behaviour ( e.g. instructions to workers to move carefully from place to place or to adopt a 
  safe  , unhurried displacement , avoiding short - cuts ) , this action can not meet the 
 requirements for preventing all oamds .
instructions of this type alone in fact disregard 
 other aspects , which are sometimes more difficult to objectify and control , such as urgency 
 of the situation , fatigue or certain task requirements . as in all occupational accidents 
 ( oas )
, an oamd will often be caused by a combination of factors , each of which is of 
 different nature .
a clearly visible obstacle is never sufficient to cause a trip : it may 
 simply not be taken into account by a worker , when his / her visual attention is absorbed by 
 his / her task during a displacement .
on the other hand , an oamd can occur without involving a 
 permanent , visible anomaly in the environment : a worker , late for his / her appointment , 
 misses a step when running up stairs that are not subject to any design defect .
finally , 
 many situations are temporarily more susceptible to oamd occurrence : for example , when 
 performing his / her activity , a worker collides with an element in his / her environment , which 
 obstructs his / her movement ; he / she had intended to move this element on completion of 
 priority work . in the situation illustrated by fig . 

1.two images of occupational situations taken from the  napo in safe on site / champions 
 of the world  video produced by , a first level of prevention would involve disposing of unwanted material or 
 organising storage areas . at a given moment , presence of elements required for performing a 
 task can also represent an accident factor for a worker or his / her colleague . in fig .
1b , this would be the cinder blocks left near a 
 mason , but could also be a batten left lying on the ground when stripping formwork , a 
 wheelchair when transferring a patient or a toolbox when conducting maintenance work .
two images of occupational situations taken from the  napo in safe on site / champions 
 of the world  video produced by   neutralising accident factors that are permanent and visible in the work environment is 
 important , but analysing the part played by this factor in a more comprehensive accident 
 genesis is in fact just as important .
behaviours adopted in work situations also need to be 
 understood since they often reflect the presence of organisational factors .
the literature includes in - depth analyses of occupational slips , trips and/or other 
 movement disturbances conducted at various companies .
events leading to injury are integral 
 to the relevant company operation and some are related to production - safety arbitrations 
 referred to long ago in the general occupational accident field .
for example , situations 
 described in terms of  recovery  or  momentary co - activity  by faverge10 reflect arbitrations revealed during iron mine accident 
 analysis , in particular .
monteau11 refers 
 to  known organisational risks  , when analysing occupational health and safety from an 
 organisational perspective .
it should be noted that few of these accidentology studies are 
 considered in relation to understanding and preventing oamds . yet
, the contribution of 
 multiple organisational factors has been highlighted during analysis of such accidents .
research reported in bentley & haslam12 and in leclercq & thouy13 questions the role of work preparation in stfa occurrence .
bentley 
 & haslam12 effectively describe the 
 difficulties encountered in distributing mail on time during periods involving snow and ice . 

leclercq & thouy13 show that a number 
 of accidents have involved field operators climbing up into and down from trucks , when 
 checking equipment required during the day at various building sites .
this phase of their 
 activity called for all the more care since instances of missing equipment were 
 frequent .
a specific study of oamds sustained by train drivers14 has revealed problems involving task allocation as well as recovery 
 situations , i.e. situations in which  the normal task is interrupted by an incident , from 
 which the worker has to recover , in other words strive to restore the usual course of 
 work10 .
these 
 accidents occurred when inspecting a train prior to departure : in the first case , the train 
 started to brake during the operation ; in the second case , an inexperienced driver detected 
 a brake failure he had never before encountered and did not know how to remedy and , in the 
 third case , the driver once again climbed down from the train because he had overlooked an 
 inspection point . in each case , the driver gave his full attention to inspection in order to 
 prevent the train being delayed and , when walking , tripped on a sleeper or a plate creating 
 unevenness in the ground .
in the first two cases , the driver was performing a recovery 
 operation at the time of the accident to restore the train braking system operation .
all 
 recovery situations introduce or accentuate a time constraint , so resources mobilised to 
 make the braking system operational as quickly as possible were partially lacking in terms 
 of controlling displacement and this effectively caused the driver to trip .
bentley et al.15 refer 
 to a  concurrent visual task  when explaining the occurrence of certain oamds ; these authors 
 also emphasise that , at a given moment , resources dedicated to performing the task may be 
 lacking in terms of controlling displacement . in many cases , existing obstructions
to displacement are due to earlier or simultaneous 
 work performed by workers other than the worker , who sustains an oamd ; this reveals the part 
 played by co - activity or a succession of activities in oamd occurrence .
for example , a 
 worker has to divert to avoid tools useful to other workers installing new equipment , but 
 left on his / her displacement route .
displacement diversion may be considered as a form of 
 recovery activity intended to restore a normal course of work by returning to the initial 
 route .
co - activity , historically described by cuny16 , represents task performance by persons pursuing different 
 production objectives and required to share concurrently a common workplace .
interim 
 situations or those involving subcontracted work , in particular , can generate co - activity or 
 a succession of activities .
finally , bentley & haslam12 have 
 shown that the  job and finish  policy implemented at the time in the united kingdom s mail 
 distribution company , which allowed workers to go home as soon as the last mail had been 
 distributed , could encourage workers to take risks by hurrying or taking short - cuts .
these 
 authors reported that workers explained that the accident risk raised by reading mail 
 addresses while walking was more acceptable than the time wasted in stopping to read the 
 addresses .
working conditions ( hence movement performance conditions ) play a part in oamd occurrence 
 since they make it more or less difficult to control displacement and , more generally , 
 movement during task performance .
organisational factors highlighted during oamd analysis reveal worker arbitration between 
 production and safety in the work situation , in which he / she is exposed to a risk of 
 movement disturbance .
production - safety arbitrations relate particularly to the 
 organisational activity implemented by the company .
neutralisation of organisational factors 
 therefore requires local and collective management of the oamd risk to ensure proximity to 
 the company s specific characteristics and to compare existing logics and viewpoints . 

bentley & haslam12 state that , 
 depending on the workers distributing mail , managers consider performance a priority over 
 safety and that the workers themselves prefer rapid performance to safer performance of 
 their work ; their attitudes reflect those of the management in this respect . as in the presence of any oa risk
, controls are implemented to perform the task , while 
 ensuring safety with regard to movement disturbance , in other words while ensuring movement 
 control .
, for example in the case of a collision when bolting because the 
 spanner slipped .
oamds can also involve more atypical movements , such as picking up an 
 object or walking , and in some cases , being cut by an element in the environment or missing 
 a step when running up stairs .
controls implemented in work situations are therefore 
 virtually permanent and the worker manages the available resources to perform his / her task , 
 while controlling his / her movement .
the resources required for movement control vary in time 
 and with respect to the work situation .
for example , derosier et al.17 report situations , in which metallurgists 
 are sometimes required to move over template elements similar to beams . at these moments , 

the resources required to control their movements are more extensive than those required 
 when walking on a level floor .
likewise , resources required for walking on a floor with 
 variable slip resistance are more extensive than resources required for walking on a surface 
 with uniformly high slip resistance .
resources needed to perform the task as a whole are 
 also variable . at certain moments ,
a worker s visual attention can be taken up by a task and 
 can thus be unavailable for movement control14 , 15 .
task characteristics and requirements 
 will therefore condition resources , which could be dedicated to movement control .
2.model of ostfa understanding based on the worker and his / her activity ( adapted from 
 the model developed by vezina ( 2001 ) for musculoskeletal disorders )
. contributes to our understanding of movement disturbance by illustrating a work 
 situation model based on the worker and his / her activity .
this has been adapted from the 
 model developed by vzina18 in relation 
 to work - related musculoskeletal disorders ( wrmsds ) .
wrmsds and oamds are invariably outcomes 
 of occupational risks , which manifest themselves through worker movements .
this is why oamds 
 and wrmsds possess common characteristics with an impact on prevention .
oamd prevention has 
 been the subject of little research to date and could therefore benefit from studies in the 
 wrmsd prevention field , at least from a theoretical and methodological standpoint .
similarities between wrmsd and oamd and their 
 consequences for prevention have been developed by leclercq et al4 .
model of ostfa understanding based on the worker and his / her activity ( adapted from 
 the model developed by vezina ( 2001 ) for musculoskeletal disorders ) .
figure 2 shows that controls are implemented in 
 work situations to ensure safety when performing a task .
movements performed at work are subject to continuous 
 adjustment with respect to the required task and individual , organisational and 
 environmental constraints , as reported by chassaing19 when studying wrmsds . some of the implemented controls can be 
 easily observed ( rushing , moving round obstructions , etc . ) and the individual strategies , to 
 which these controls contribute , can be examined in detail using personal interviews .
sometimes , they 
 can not be visually observed and their detection requires a very fine observation grid : one 
 that accurately describes movements such as heel strike angle when walking , distance 
 provided as a safety margin between the foot and a low - level obstruction during a 
 displacement , supports used , etc . to acquire a best possible understanding of worker controls implemented to perform a task 
 in an occupational situation ,
while avoiding movement disturbances , we need to combine two 
 levels of analysis : analysis of the activity and analysis of the movement performed within 
 the activity .
macroscopic developments such as technological advances or the advent of regulation 
 influence the conditions under which an operator performs his movements and hence the 
 resulting risks present in occupational situations .
this model illustrates the outcome of macroscopic 
 developments in the occupational situation through productive organisation 
 choices . illustrates a work organisation model developed by the niosh20 .
the nature of the different factors involved in oa occurrence is displayed , along with the 
 boundaries within which these factors are effectively harmful .
organisation of the niosh work model taken from sauter et 
 al . , ( 2002 ) .
this model illustrates the outcome of macroscopic 
 developments in the occupational situation through productive organisation 
 choices . in general , productive organisation characteristics evolve constantly under the specific 
 effects of technical progress ( automation , introduction of new technologies , etc . ) , 
 subsequent growth in productivity21 , 
 employment market developments ( active population characteristics , etc . ) and 
 reorganisations22 ( outsourcing , etc . ) . 

these macroscopic developments and choices made by productive organisations affect the work 
 situation ( level of prescription , time and spatial constraints , etc . ) in ways that condition 
 how worker movements are performed .
controls are continually implemented not only by a worker performing his / her task , while 
 avoiding injuries , but also at the different levels illustrated in fig .
3 . analysing and combining these controls contributes to our 
 understanding and prevention of occupational accidents , in particular oamds .
despite scientific progress in the safety field , oamds are still commonly considered 
  simple  accidents resulting from a malfunction in a  simple  system ; this might suggest 
 that their prevention is also 
this paper aims to encourage changes in these 
 perceptions by attempting to orient the reader s vision towards organisational factors , 
 which often combine with other accident factors to cause movement disturbance and injury in 
 work situations .
these risks manifest themselves in the worker s movement but are none the 
 less an unwanted consequence of productive organisational decisions .
oamd organisational 
 factors reveal the need for local and collective management of this risk and the importance 
 of a better understanding of movement / displacement performed under working situations , i.e. 
 in a context integrating specific task requirements and working conditions .
while organisational measures implemented by the company represent a lever for oamd 
 prevention , two points should be noted : on the one hand , organisational activity is 
 restricted as illustrated by fig . 3 and , on the 
 other hand , its lever is not unique .
maximum possible neutralisation of factors close to the 
 injury in the accident genesis and risk awareness also constitute major lines of prevention . 

awareness of the oamd risk , in particular , is an essential prerequisite to any progress in 
 preventing these accidents .
perception of the oamd risk and its more or less  accepted  
 nature are factors , which determine both consideration of this risk at every level of the 
 company and controls implemented by workers .
 workplace design and upkeep , or human factors , are frequently advanced for explaining 
 so - called occupational slip , trip and fall accidents ( ostfas ) . despite scientific 
 progress , these accidents , and more broadly occupational accidents with movement 
 disturbance ( oamds ) , are also commonly considered to be  
 simple  . 
 this paper aims to 
 stimulate changes in such perceptions by focusing on organisational factors that often 
 combine with other accident factors to cause movement disturbance and injury in work 
 situations . 
 these factors frequently lead to arbitration between production and safety , 
 which involves implementation of controls by workers . 
 these controls can lead to greater 
 worker exposure to oamd risk . 
 we propose a model that focuses on such controls to account 
 specifically for the need to confront production and safety logics within a company and to 
 enhance the potential for appropriate prevention action . 
 these are then integrated into 
 the set of controls highlighted by work organisation model developed by the niosh . 