The most important output of the workload assessment is the workload profile: this
is a description of the workload overall and will specifically refer to demand factors
that contribute to the individual’s perceptions of effort.
In order to develop a profile you will need to provide some commentary on the results
from each of the tools used. It is not sufficient to simply report the findings.
Below is guidance on the things to consider when reviewing the data from each tool
and then some prompts to help structure the workload profile.
When reviewing the ODEC data a useful rule of thumb is to look for an approximately
equal split of elements between high, medium and low. This would appear to suggest
a reasonable balance for a system to be controlled. Greater than 40% of elements
within the high category should suggest caution about adding any further elements
to a system without compensatory actions.
It should be noted that IWS is a subjective score and should never be used on its
own to make judgements about workload. As a self-reporting subjective score it is
susceptible to factors other than workload. For example, experience indicates there
is a tendency to give relatively higher ratings if the workload assessment is being
conducted in relation to complaints about workload or requests for a meal break.
As a starting point, IWS ratings of 4 or more may suggest that the system and working
environment is or is about to demand considerable effort from the signaller. This
may be sufficient to cause observable deterioration in signallers completing all
activities required of them within the necessary time available. However, this is
an indication only and should be considered in the context of:
- The range of IWS scores from different signallers (i.e. do they all follow a similar
pattern or are they significantly different?)
- The pattern of scores over the assessment period (i.e. how does the scoring vary
and why?)
The advantage of using IWS data with activity analysis data is that the activity
analysis should provide a greater richness to the IWS and some indications about
why the scores are as they are.
Calculating the mode or frequency with which each rating was selected over a period
of time will reflect the most frequently scored rating and are the most appropriate
scores to report. Calculations of a ‘mean workload score’ are misleading
as they do not represent the dynamic nature of the IWS outputs.
The AAT provides information about the percentage of time that an activity occupies.
This is useful information to understand the implications of time pressure as a
dimension of workload. However, activity occupancy is not synonymous with workload
as there is not always a direct relationship between actions, events and workload.
The AAT cannot account for the demand created by the combination of certain activities
and it cannot account for unobservable events such as mental processing, which may
vary independent of the observable actions and events within the job.
The use of the AAT in conjunction with other workload tools (ideally IWS and/or
the SME Commentary) provides a more comprehensive understanding of signaller workload.
In particular the SME commentary can provide some interpretation of the nature of
the work being completed by the signaller and more insights about the acceptability
of that work.
The use of the Workload Principles is generally at the beginning and/or end of an
assessment as a way of providing an overview of the workload issues. They do rely
on the judgement of the assessor to state whether each principle is fulfilled or
not.
Principles 1-5 and 9 are primary principles and are essential for safety and performance.
The remaining secondary principles are desirable. If it is apparent that these are
not achievable then further investigation would be necessary, although failure to
meet the primary principles would obviously take greater priority.