"A tailor-made shift system should be a compromise between the
employer's goals, the wishes of the employees, and ergonomic
recommendations for the design of shift systems."
(Changing Schedules: Shiftwork by P.Knauth,Chronobiology
International, Volume 14, Issue 2 1997)
It has to be realized that
there is no ideal shift system which is going to fully meet an organizations
needs and the individual health, social and family needs of each and
every employee.
As far as Policing is concerned the goal is to deploy the available
and limited resources as efficiently as possible so as to provide a
24/7 response to calls from the public. In order to do this Police
managers need to analyse the demand for calls for service from the
public - see attached
Demand Graph.
Having analysed and established when and what the demand is, the next
stage is to design a shift pattern which best matches resources to demand
by putting the right number of officers on duty, in the right place
and at the right time
When designing a shift system there are a number of variable parameters
to be considered. These include whether fixed or rotating shifts,
direction and speed of shifts, lengths of shifts and starting times
of shifts. There are also various constraints to consider such as
the Working Time Regulations and Police Regulations.
Extensive research into shift work and the effect it has on the health
of shift workers has resulted in a set of ergonomic recommendations
which should also be taken into account when devising
shift patterns. These recommendations include:
minimise permanent nights;
minimise sequence of nights:
only 2-4 night shifts in succession should be worked;
consider shorter night shifts;
avoid quick change-overs;
plan rotas with some free weekends;
avoid overlong work sequences;
Rotate forward (ie clockwise
rotation morning/ evenings/ nights);
Avoid early starts.
(Guidelines For Shiftworkers, Ed.
by A. Wedderburn, Bulletin of European Studies on
Time, 1991).
Fixed shifts cause
the least disruption to circadian rhythms, provided
that the workers maintain the same sleep/wake cycle
on their rest days as on their work days. However,
most night workers revert to a normal day/night cycle
on their days off to participate in family/social
life, thus negating any adjustment in circadian
rhythms. Fixed shifts are popular with Police Forces
in the United States where Officers 'bid' for shifts
according to their seniority.
Slowly rotating shifts
allow greater time for circadian rhythms to adjust to
each new shift. However, this type of shift system
can result in sleep debt and fatigue due to more
consecutive periods of day sleep. Studies on
shiftworkers have shown it takes about 21 consecutive
days for circadian rhythms to fully adjust to
nightshift. Again, workers tend to revert to a normal
day/night cycle on their rest days during this period,
thus negating any adjustment which has begun.
Weekly rotating shifts have
been shown to provide insufficient time for the
circadian rhythms to adjust completely and
enough time for a sizeable 'sleep debt' to build up.
Working 4 to 7 night shifts in a row is now widely condemned by experts. Those Police Forces
which adopted the 'Ottowa' shift pattern in the early
1990 (which included 7 consecutive nights) are now
looking at VSA's (Variable Shift Arrangements) which
minimise consecutive nights.
Rapid rotating shifts
have the advantage that (i) the circadian rhythms
remain day orientated since not enough time elapses
for them to adjust to the new routine;(ii) there is
less accumulation of sleep debt; and (iii) there are
free evenings every week for social/ family contact.
The disadvantage is that when on the 2 to 4 nights of
work, the worker will be out of sync and alertness
may be affected.
Direction of Rotation:
Forward rotation (earlies/lates/nights) is
recommended from a circadian perspective because the
internal body clock naturally tends to run slow (ie
every 25 hrs). It is easier then, to delay sleep than
it is to advance it. Consider 'jet lag' - people
experience less jet lag going from east to west than
from west to east. The same principle is at work.
However some workers prefer a backward rotation (nights/lates/earlies)
because it affords more time to recover lost sleep
and prepare for the next night shift.
Early starts to the morning
shift should be avoided. Early starts reduce
sleep as, by choice or by family circumstances, most
workers go to bed around their normal time. Reduced
sleep leads to fatigue which increases the risk of
errors and accidents on the morning shift.
There is no optimum starting time -
but 0700hrs is better than 0600hrs which is better
than 0500hrs.
Consider shorter night shifts.
As mental alertness and physical performance
deteriorate during the night, it is argued that night
shift should be restricted to 7 or 8 hours to
minimise the risk of errors and accidents. VSA's
enable the Early or Late shifts to be extended
accordingly.
Minimise sequence of nights. Minimising the
sequence of nights worked minimises the degree of adaption (or
disruption) of the circadian rhythms from their normal day
orientation. Academic recommendations vary between a maximum of 2
and 4 consecutive nights.
Recent research within the Police service on this
subject was conducted by Sgt Carl Masson, Merseyside Police. His
publication 'Healthy Nights' published by the Home Office Police
Research Group goes into this in greater detail .
For a summary of the research, see the recent
article 'The Killer Shift', published in the Police Federation
magazine 'Police' in
November 2000.
Rest days. Sleep
debt does not have to be paid back "in full"
on rest days as recovery sleep is deeper than normal
sleep. However, 2 nights of unrestricted sleep after
a sequence of night shifts is recommended to recover
from sleep loss.
Designing Shift Schedules.
The design of shift systems is a complex task which
is not easily done by hand. However, there are
commercial computer shift scheduling packages
available which might assist shift designers in their
task. There are also a number of academic experts in
this field which Police managers should consider
consulting.
One such commercial package is Visual
Rota - Staff Rostering Software.
Perhaps the Police Service should be developing a
similar software package, or suite of 'best practice' shift
schedules, to assist managers and staff alike.