|Risk dormancy (RD); Multi-team (MT); Multi-team risk
|Modern industrial activities resort to MT effort. Teams are replaced
repeatedly in accordance with the work demands and progress. The
risks those teams face appear in the course of the work process,
depending on the employed tools, uncertain and often harsh
environments, and/or from exposures to risks created by the work of
other teams on site. This work could be carried out concurrently with
the work of the leading team, or by continuing the same objective or a
different task. This last scenario was identified and addressed as risk
dormancy (RD) in the earlier study of the authors . Here is a brief
review of the previous publications in the related fields.
|Sasou et al.  wrote: "Improving personal skills is important for
error prevention. However, today’s industrial plants are too large to be
controlled by individuals. Teams control power plants, aircraft, ships
and the like. However, this produces new problems. It is thought that
there are specific causes in team errors that will not be revealed by an
exclusive emphasis upon the errors of individuals. This paper has
sought to elucidate some of these factors." Hence, the authors have
indicated that there is an obvious need for an effort to investigate the
risks associated with the MT effort. The shift work or TR was
addressed recently also by NASA Safety Center-System Failure Case
Studies  in connection with the Piper Alpha disaster. The NASA
report indicates that "lack of informal “between shift” talks
compounded lax communication issues "a failure" that killed 167
workers in the world’s deadliest offshore oil industry disaster". The
consequences of this disaster were analyzed also by Reason  who
distinguished between active and latent failure: "for active failure the
negative outcome is almost immediate, but for latent failures the
consequences of human actions or decisions can take a long time to be disclosed, sometimes many years." Reason J  proposed to
concentrate, among other facets of accident causation, on the "latent
conditions" as major "organizational factors, i.e. the consequences of
top-level decision having a delay-action effect upon the integrity of
various defensive layers". These conditions contribute to both the "local
workplace factors" and to the "unsafe acts" to breach through the
defences causing an accident. Reason emphasizes the importance of
"what upstream organizational factors could have contributed to” the
local condition" by adopting a measured balanced level for both active
and organizational factors. One should focus, in his opinion, on
hazardous path ways on site. This attitude is wider, in terms of safety
actions, and considers the boundaries of the potentially active failures
and the interactive activities with other teams in the MT formation.
The techniques of identifying organizational factors that cause "latent
conditions" contribute to both proactive and investigative actions of
the risk management procedure. However, for the TR event it's neither
effective nor practical in trying to avoid a "lurking" risk created
previously in the wider boundaries of the active failure (e.g. of a failure
in the previous team action) threatening to get materialized during the
current shift work. Such an attitude provides insufficient attention for
TR and its effect on safety. When it comes to the influence on RD time,
which is the outcome of MT risk dormancy (MTRD), such an attitude
is even more deficient. Mitropoulos et al.  call for a "future direction
and research needs" and suggest to “developing effective team process
for team within and between crews". Mitropoulos et al.  identified
the taxonomy of accidents that considers the "unrecognized hazard” as
“another type of accidents” that “involves situations where the worker
is exposed to a “hidden” hazard.” The hidden hazard can be a
component near its functional limit (such as, e.g., an unsecured deck)
or a normal behaviour (such as, e.g., walking on the deck) that might
release the hazard. The hidden hazard could be created by an error
made by a previous crew. This situation has to do with some issues
addressed in the present paper, with an emphasis on the solution for the critical event of TR. An innovative approach to the analysis of the
occupational safety was recently suggested based on a holistic
perception of MT interactions. The approach is aimed at the means to
avoid mistakable actions, which could lead to dormant risks. Farag 
The term “RD” is identified as "the time delay between the occurrences
of a failure (hazard event) in the action of one team (team A) that
affects another team (team B) involved in the process" (Figure 1). The
authors analyzed the time aspects of RD in MT work and proposed a
model for risk evaluation and management based on the assessment of
time-dependent probability (TDP) .
|MT includes various aspects of the processes of teamwork
interaction, such as different professions and expertise of the teams on
site, with consideration of the periods of time to perform the job. To
successfully fulfil a task, teams need to be replaced by shift work
system in order to avoid repetition of what they do by other teams.
When a team reaches the work site and "assumes command", its first
task is to get prepared for the job: assign qualified personal, choose the
right tool (s), receive training, get instructions, etc. All these activities
are critical to safety. TR event is certainly a crucial safety factor: teams
are required to conduct in advance various safety actions, such as, e.g.,
hazard identification, evaluation and control for all the job stages to
insure safe performance. TR risk evaluation applies to all the
potentially hazardous situations that might threaten the team
members. Such situations include dormant risks generated by previous
teams that have been active on site. The RD range is the time interval
between hazard creations up to MTRD accident. This time span should
contain at least one event of TR. Obviously; any injured by-MTRDaccident
team starts either at "workday" beginning or at TR (Figure 1).
|The major concern of this study is the effect of the TR event on RD,
in a situation, when this team is involved in a MTRD accident. While
the teams involved in MTRD accidents have been identified earlier, the
TR event occurrence time still needs to be determined. Therefore, an
appropriate classification scheme for team's appearance according to
their sequence in the RD range is suggested to assist in determining TR
types. The MTRD accidents of public utility (PU) are sorted out
utilizing the following MT classification criterion. Let us examine the
classification of MT formation with regard to TR events followed by
several particular and typical examples highlighting their
characteristics to understand better the significance of the
|Nowadays work is characterized by numerous teams acting on site,
i.e., by the MT effort to accomplish the job. These teams are assigned to
execute the work in different attendance and in different succession.
Although the term "MT" refers to all teams working on site, it should
be noted that MT's have different characteristics affected by the
particular team duties that contribute to the dormant risk. When it
comes to the evaluation of the influence of TR event on the RD, greater
attention should be drawn to the characteristic of teams regarding
their roles in the MT. Our analysis is intended to assist in the
determination of the time of the occurrence of a TR event. This
consideration leads to the following classification of the team
appearance on site. Three different categories were detected (Figure 2).
|First, Imminent MT (IMT): Team's work in succession of several
hours or in a 24 hours cycle shift-work. IMT is characterized by a task
that depends on the same mission with no ability to switch between
teams. For example, first of the utility lineman teams performs
electrical disconnection, followed by a second team that repairs the
|Second, Repetition of MT (RMT): Teams works in a shift-work
schedule at a longer than 24 hours’ time span (such as 9- to-5 shiftwork
schedule), i.e., carries out work that needs more than one shift to
accomplish the given job or a particular stage of a permanently
|Third, One-time MT (OMT): Team's work carried out just once in
the project or during a long period of time between certain tasks. For
example, teams performing tests, such as grounding test or taking
samples during concrete casting, or installation of roller shutter in
inner rooms or in factory halls.
|Example: An aerial work platform (AWP) is widely used in public
utility (PU) in Israel for maintenance and construction of all types of
power plants and overhead lines. At a power plant construction site a
70 m long AWP telescopic hydraulic arm is used to provide temporary
access for installation of panels to provide closure of air intake filter in
a gas turbine. AWP stabilization stage is carried out using four
hydraulic stabilizers. One of them was mounted on rubble, which
covers the main transformer oil concrete area, assuming that it is a
rigid gravel surface. The rubble could not carry the stabilizer pressure,
which fell down into the arrest openings. Damage was caused to the AWP, and the workers who operated it were injured. Two weeks earlier
the team that performed the rubble spreading over the arrest openings
marked this place with a warning tape, but failed to inform the project
manager regarding its instability. An unstable ground risk was neither
estimated nor identified, so that MTRD stayed dormant for two weeks.
However, the team used the AWP when they started their job at the TR
event and was able to identify the risk by conducting job safety analysis
(JSA)-risk evaluation procedure. As a result, they could increase the
likelihood of correctly identifying this risk by placing a warning tape
or by receiving this information from the project manager on site. This
example illustrates the importance of managing RD in MT by using TR
event as a critical point regarding controlling those risks. This example
illustrates the significance of a TR event for safety at a point in time
when work slows down, or stops completely for a while, for risk
|The reported accidents data of five operational Israel Public Utility
(PU) divisions compiled by its safety department during 2004-2011
show as much as 9% of all accidents are of MTRD character showing
significance of this type of accidents shown in Table 1.
|The RD time span between hazard event created by Team A and
accident occurred to Team B is necessarily divided by TR event.
Therefore, it's important to analyze the statistics of TR event in this
|Farag , *MTRD: "Teams often operate independently, with no
explicit functional linkage between them. In other cases, more or less
close professional collaboration is required to perform a particular
task. For example, repair work in an electrical utility typically requires
involvement of several teams. One team of electricians disconnects the
power, another team repairs the damage, and a third team is deployed
outside the secluded site, often on a standby basis, to assist, if
necessary, the workers inside the worksite. In this example three
different teams perform various aspects of the work aimed at a
particular mutual goal. A mistake, error or a failure in one team's
actions affects other teams involved in sequential large-scale activity,
and has a potential to create a hazard. The hazard might remain
dormant for some time, but eventually can become or generate a risk.
This risk might have an immediate impact on the team member who
caused it, and/or threaten another team continuing the job at the given
site. This scenario can be identified as risk dormancy (RD). When
occurring in a multi-team situation, it becomes multi-team risks
dormancy (MTRD)" see also Figure 1.
|This analysis is aimed to provide a statistical assistance to safety
manager to pay attention for the following stages around TR event: (a)
increased probability of hazard creation and (b) zoon of increased
likelihood of MTRD accident.
|TR effect analysis
|TR in RD range: The TR event that appears at the RD range between
creations of a hazard event by Team A to its realization is crucial for
Team B regarding the required treatment. The reason is that a certain
MTRD accident might lead to an injury. An analysis of the RD path
with respect to TR event reveals the following stages leading to an
accident refer Figure 1:
|T0 -Beginning of activity which in high likelihood generated a
hazard event becoming a risk threaten team "B".
|Td-Continues dormant time
|Tacc-RD time at accident
|Here the DT-Td, eq (1), is a random variable extending between the
beginning of Team an activity T0, which could possibly generate a
hazard event TR, and the accident RD time at accident-Tacc. Thus, the
entire RD range can be expressed by DT-Td. This analysis addresses the
effect of TR event on RD and proposes an effective model for the TR
distribution, treating TR as a random variable. In this context,
classification criteria for RD are related to risks generated by MT
|Probabilistic analysis of TR effect
|TR event distribution: Two intervals of DT extend along the RD
range until an accident takes place. Firstly, the DT interval extends
from a hazard event creation until TR event-TTR. In the following
analysis it is limited to T0˂Td ≤ TTR. Secondly, the DT interval extends
from TR event until the accident-Tacc. In the following analysis it is
limited to TTR˂Td ≤ Tacc. Start and end times T0 and Tacc of the RD
range are known in advance . Accordingly, the team affected by the
accident and the accident time, as well as the team that generated the
risk (risk-causing team) and the time of an activity, when the risk was
actually generated, are determined. Moreover, once the MT work
sequences of events are established including the affected team, the
time when these teams start working can be determined (Figure 2).
One can therefore calculate the occurrences of TR events that occur
within the RD range between T0 and Tacc.
|Example: Linemen team from North District start working at TR 10
AM, average DT-dormancy time is 4 hours. The first interval of
increased hazard creation by team of electricians whom disconnect the
power is around 07:30 AM while the second interval of increased
accident probability is around noon (12:00).
|Considering MT layout of an organization or a project, multiple TR
events will take place in a continuous DT (Figure 3 and 4).
|TR event distribution over RD range: Once the TR event nature has
been determined (in accordance with the previously conducted
analysis), a probabilistic model can be developed by taking into
account the TR moment of time-TTR that is expressed by the
continuous random variable DT-Td. We suggest a triangular
distribution with maximum at an actual TR moment as a proper model
for this pdf-pTR(Td) as shown in eq. (2).
|pTR (Td)=2Td/TaccTTR0˂Td ≤TTR+2/Tacc [(Tacc - Td )/( Tacc – TTR)]TTR˂Td˂Tacc → (2)
|pTR (Td ) is the probability density function (pdf) of the random
|Tacc-RD time at accident
|The pdf function as shown in eq. (2) is for a single TR event.
However, to create an experimental function for a plurality of TR
events and to adequately fit all data, a Procrustes’ procedure is applied
for relative DT as a continues variable - τ:
|fexp(τ, Tacc ,TTR) = 2(τTacc/TTR )τ ≤ TTR/Tacc + (1 - τ)/(1 – TTR/Tacc) TTR/Tacc˂τ˂1 →(3)
|= Td / Tacc is the relative dormant time
|To represent maximal sample statistical data for TR an averaging
procedure over all available events could be used:
|f̅exp(τ, Tacc ,TTR) = ∑ i=o,nfexp[τ, Tacc ,TTR]i /n →(4)
|Results of five cases (five divisions of the PU) where fitted using
|f(τ, α,β) = Г(α + β) / Г(α)Г(β) τα-1 (1- τ)β-1 (5)
|The fitted parameters for the five public utility (PU) divisions are
shown in Table 2.
|The data are well described by Beta distribution and the computed
data are shown in Figures 5-9.
|Modern industrial projects are based on involvement of teams.
More teams mean more TR events. These events cause slowing down
the work and even sometimes stopping it as part of early new team
preparation and the risk evaluation at the work site. Therefore, TR is
an event that should be considered critical. It is a sort of an "Achilles'
heel" of safety compliance. The following considerations seem to be
|MT work emphasizes the roles of the team, which created the risk,
and the affected (injured) team after TR. Once a potentially hazardous
event is created and identified, the likelihood that it will actually occur
within the RD range, the TR should be addressed and their likelihood
|TR events are interfaces between the working teams and have a key
effect on the risk and the likelihood of its successful and trustworthy
evaluation. It is important that the TR events are quantified as critical
safety factors. In the RD range at least one TR event occurs between a
hazard event created by one team and accident that harmed another.
|The TR event that takes place within the DT range is described in
our analysis using triangular pdf. Note that Johnson  indicated that
the TR event over RD interval is limited by two points-T0 and Tacc.
Normalization of the dormant time range is done in our study by using
Procrustes procedure and setting a new scale spread between 0 to 1
instead of T0 to Tacc one .
|Once a model for the single TR event is determined, averaging was
conducted over all events. This continuous distribution can be fitted
with beta distribution.
|The following are the main finding of this paper: firstly, in the
modern MT work over the RD range, a TR event represents a
potentially risky point to safety. Secondly, The analysis of the fitted beta
distribution reveals that pdf maximum (mode, most likely value)
appears at the time TTR, where TR event located at approximately 40%
of DT dividing the DT in proportion of 2:3.
- Farag E, Ingman D, Suhir E (2015) Managing Risk Dormancy in Multi-Team Work: Application of Time-Dependent Success-and-Safety Assurance Methodology Theoretical Issues in Ergonomics Science.
- Sasou K, Reason J (1999) Team errors: definition and taxonomy Reliability Engineering and System Safety 65: 1–9.
- (2013) Nasa Safety Center-System Failure Case Studies 7.
- Reason JT(1995)Understanding adverse events: human factors. Quality in Health Care. 4:80-90.
- Reason JT (1997) Managing the Risks of Organizational Accidents. Aldershot: Ashgate Publishing Ltd.
- Mitropoulos P, Memarian B (2012)A Framework of Teamwork Attribute Afeecting Workers Safety. ASCE.
- Mitropoulos P, Howell GA, Abdelhamid ST (2005) Accident Prevention Strategies: Causation Model And Research Directions. ASCE.
- Abdelhamid ST, Everett JG (2000) "Identifying Root Causes of Construction Accidents". Journal of Construction Engineering and Management, ASCE 126: 52-60.
- Johnson D (1997) The triangular distribution as a proxy for the beta distribution in risk analysis. Journal of the Royal Statistical Society 46: 387-398.
- Folkard S, Tucker P (2003) "Shift work, safety and productivity" Occupational Medicine 53: 95-101