Aspectos éticos

The questionnaire results demonstrate that Tyne & Wear Metro drivers do not have concerns about effects of design of the physical environment, considering the current

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operational procedures as sufficiently safe. Nonetheless, the literature advices that the next step in state-of-the-art accident causation research will be an in-depth look in what is considered “normal” operations and performance (Salmon et al., 2015).

Something considered safe can be deemed risky under a scrutiny. Furthermore, as with most questionnaire studies, there are always concerns about respondents’

honesty and openness even though a lot has been done to induce it in this survey.

Even though the results mostly corroborate the findings of the past incident analysis, several unusual results were found. Those can be mostly attributed to the

participants’ assessments of the statements and their answers in the rest of the questionnaire. It is possible that the statements were not worded correctly. The attempt to vary wording of similar questions might have introduced a difference in ways how the participants perceived a situation described in a statement.

Furthermore, it is possible that the drivers have failed to associate themselves with some statements due to lack of particular experience, survey time constraints and other factors. The above expressed concerns about openness also apply here as the participants could have been biased in order to show their confidence and good level of knowledge. When the questions were non-personal, e.g. marking questions, the drivers might be more inclined to give unbiased answers.

Fisher’s exact test was used to see whether answers in the marking questions influence participants’ attitudes towards some of the statements. Even though several statistically significant relationships exist none of the expected ones are significant, e.g. relationship between the GPL marks and statements 18, 25 and 26.

This demonstrates that the drivers approach these questions with separate mind-sets and see different underlying structure to those.

It is important to explore ways how to investigate drivers’ interaction with the physical environment without biases introduced by drivers’ willingness to express certain agenda or lack of it. When assessing the questionnaire, a driver has enough time to consider what his/her answers can achieve or what consequences those might have.

Moreover, a retrospective assessment of a situation can be different to a real-time one. Hence methods that would provide insights into drivers’ performance in real time should be explored. Moreover, these methods should be non-intrusive and facilitate real-time driving process without major alterations in order to avoid different types of statistical errors. One of the methods, which suits this description is eye-tracking when drivers’ performance is assessed based on their gaze patterns.

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6.5 Conclusions

This chapter presents a collection of drivers’ attitudes towards specific design features implemented in Tyne & Wear Metro. Many of these elements are used in other urban rail systems in one form or another which allows transferability of the results and methodology. Some of the elements are considered for implementation, e.g. DOO operations. The results provide good overview of drivers’ assessment of such features and associated PSFs.

The approach of providing drivers with specific hypotheses based on previous research helps identifying links between different PSFs. The questionnaire results show high level of agreement with the hypotheses set from the historic incident data.

Moreover, the findings are often in line with wider human factors research corroborating similar failure mechanisms to other safety related industries.

Correlation can be seen between the drivers’ selected causal factors and results of previous work in the area. The participants confirm that many features of the

immediate physical environment in Tyne & Wear Metro have relatively low

satisfaction levels. The main differences with the previous human factors research are found in areas of monotony of a task, effects of experience levels and tunnel exit/entrance.

Even though the drivers generally do not believe that there is a risk associated with the offered statements, it is definite that the respondents can discriminate between elements of the system design in terms of ergonomics. There are concerns about drivers’ being able to answer “personalised” statements with full honesty due to discrepancies in assessment of different elements. However, it is possible that even the lowest marked elements are still considered safe but not in comparison with other elements.

Researchers in human factors start focusing on “normal operations” in order to reveal potentially hidden incident causation factors. Discrepancy between some contextual statements and marks demonstrates that drivers might not be able to assess the situations offered in the questionnaire due to method limitations. This strongly implies that further work should be pursued on a cognitive level, where drivers’ statements (from this chapter) are compared to their actions. Such comparison will not only provide an additional dimension to the above results but also can reveal hidden causal mechanisms which could be overlooked in the questionnaire study. Moreover, it is necessary to understand whether drivers’ discrimination between similar

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locations is driven only by personal and organisational factors, or there are small design discrepancies which affect that too.

The results highlight a number of areas with future research potential. In terms of design features and with historic incident composition in mind, station layouts show high potential of safety improvements if associated PSFs are investigated. Different station types, positions of running signals and DOO equipment are some of the

areas, which should be prioritised for research on a cognitive level. Other avenues to explore include environmental effects on DOO infrastructure, reduction of noise and other distractions in a cab, door controls. Sequence and duration of speed limits should be given consideration too. Signalling types need to be studied further in terms of usability and ease of use. Passenger levels and associate distraction show significant importance on drivers’ performance in different (not only station-related) safety-critical tasks.

The questionnaire demonstrates importance of drivers’ personal experiences in assessing different situations. Previous incident involvement often makes drivers more critical towards adverse effects posed by the physical environment. It is important to learn more about this relationship in order to explore its potential inclusion into a driver training process. Furthermore, this work shows that metro systems could benefit from raising awareness of the risk-bearing locations among the front line staff. Such awareness should improve the existing route knowledge but should not be overbearing to avoid shifting a focus of the safety-related performance only to certain poorly performing locations. Finally, concerns about drivers’

experience and confidence with a degraded system and non-routine operations are corroborated. It is clear that route knowledge can be reinforced by driving experience in a degraded system as well as improved situational awareness.

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