Performance of barrier systems and functions in the construction industry

This study characterised Spanish construction accidents via identified circumstances, the barriers and barrier systems and the specific ways each of the barriers functioned.

241 investigation reports were evaluated.

They cover some research on barriers and barrier systems – noting there’s various models and definitions based on perspective. One way to look at them is safety barriers are physical and/or non-physical means to prevent, control or mitigate unwanted events whereas the barrier system performs the barrier functions.

Another perspective looks at barriers as what they do versus what they are. Other perspectives include dividing barriers into physical or non-physical and for the role of the barrier: passive or active, and physical, technical or human barrier systems.

Another perspective comes from Hollnagel and was the type used in this study, who classified barriers systems into: (quoted directly from p.10)

·      Physical or material barrier system. A barrier that prevents an event from occurring or mitigates the effects by blocking the transport of mass, energy or information from one location to another.

·      Functional Barrier System. A barrier that creates one or more preconditions that must be met before an action can be carried out.

·      Symbolic Barrier System. Barrier that functions indirectly through its meaning, which requires interpretation by someone.

·      Incorporeal Barrier Systems. Non-physical barrier which depends on the user’s knowledge and is often organisationally-related.

Barriers are often based on combinations of these barrier systems.

Results

Based on this construction sample of accidents, the most dominant departure of safety barriers related to “falls of person – to a lower level” in 18.7% of cases. Other frequent factors were: “slipping – stumbling and falling of person on the same level”, and “lifting, carrying, standing up”.

In total, one out of every three accidents in the sample was linked to slipping, stumbling and falling. In a distant second was “loss of control of machine, means of transport or handling equipment, hand-held too, object, animal”.

[My thoughts: as is often the case with incident investigations, it may shift attention and excessive resources towards managing low potential failure modes and hazards while not diverting enough resources to SIFs. This is besides the point it’s easy to wait for incidents to learn instead of focusing more on normal work where the hazards exist every day.]

The authors list the distribution of barrier system failures/infringements. The incorporeal barrier system was, expectedly, the most infringed upon system at 24.9% of cases (that is, use of rules, prohibitions, social or group pressures, ethical norms etc.). The others are shown below.

In 32% of cases the investigation didn’t identify the barrier system infringement.

Looking specifically at the barrier systems – physical barriers were most frequently infringed via slipping, stumbling and falling of persons. Here, falls suffered by workers were associated largely with the absence or malfunctioning of physical barriers such as collective protection (guardrails, scaffolding etc) or individual protection (harnesses etc.)

Incorporeal barrier system were most frequently infringed due to variability in the application of following rules or process [** although in my opinion, as with the physical barrier system this finding doesn’t really explain much at all…]

For symbolic barrier systems, failures in signposting was frequently identified.

More interesting in my opinion is that “41.27% of the barrier functions “did not perform as expected” (code c) and even 37.21% simply did not exist (code d) and were included in the research report as a suggested improvement after the accident” (p15).

However on the above finding – the authors suggest that while this may be a legitimate finding, it may also partially be an artefact that only full-fledged accidents were included in the sample rather than near misses (which may have included more examples of barrier systems functioning correctly).

Discussing some of the findings, it’s noted that in the case of physical system infringements (such as falls), two out of three cases involved the absence of a system that restricts or prevents movement. Although in some cases this may have been related to inadequate or non-existent use of PPE like fall arrest equipment, PPE should largely be the last resort and higher-order controls should be in place to eliminate or mitigate those hazardous situations.

For symbolic and incorporeal barrier system infringements, these are noted to be “widespread in a modern society, requiring cognitive interpretation by an individual in order to fulfil its purpose” (p17). Although behavioural factors are often cited as explanatory factors – it’s likewise important to highlight other structural and organisational factors like production pressures, resource scarcity, goal conflicts etc.

They suggest that one focus should be on facilitating the automatic assessment of how accident scenarios and barrier system failures propagate over time.

They say that the infringement of a safety barrier “is rarely the cause of an accident, improving the knowledge gained about the mechanism of performance in the construction industry provides important information that helps to design and implement appropriate barriers to stop the propagation of unexpected events” (p19).

Importantly, they highlight that we should focus our efforts not just largely on the failures, but rather the entire performance spectrum involved in daily work in complex sociotechnical construction settings.

Concluding, they highlight that barriers should not only prevent undesirable states but also protect against their consequences. Thus, “barrier systems and their functions should be both barriers to and facilitators of variability” (p19).

Authors: F. Salguero-Caparrós, M. Martínez-Rojas, M.C. Pardo-Ferreira & J. C. Rubio-Romero (2022). International Journal of Occupational Safety and Ergonomics.

Study link: https://doi.org/10.1080/10803548.2022.2055867

Link to the LinkedIn article: https://www.linkedin.com/pulse/performance-barrier-systems-functions-construction-ben-hutchinson