RECOMENDACIONES

The mirrors are the main area of visual attention (based on TFD) at all stations but Heworth. At Heworth the participants look at the platform for longer times than any other AOI. This is the station with the second highest passenger loadings among all selected locations. It is also the only station where the mirror is on the same side as the platform. Such layout means that the mirror can be obscured by passengers until later into an arrival timeframe. It is also possible that the two AOIs receive some error fixations due to being very close together. The overall statistics from other stations shows that the drivers use mirrors to determine a stopping point otherwise looking on those for so long is pointless on arrivals. It is necessary for them to select a stopping position that allows carrying out departure procedures safely, e.g. good visibility of the platform-train interface.

The drivers approximately spend 30% of their 15-seconds arrival sequence on either saccades or looking outside the AOIs. These outside areas could be a track, scenery or in-cab indicators. However, the more built up stations (Heworth and Gateshead Stadium) show higher TFD on all four AOIs, showing that the scenery fixations could account for up to two seconds at overground locations. Tyne & Wear Metro stations differ in terms of openness feel. The results of T-test confirm that there is a difference

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between open and confined layout stations. More condensed grouping of the AOIs influences the TFD due to reduction in saccadic movements and transition time between the design elements.

For open layout stations (Pelaw and Felling) a stopping position marker becomes the second most looked at AOI. According to GI/RT7033 (Railway Group Standards, 2009) the recommended dimensions for platform stop markers is only 300x250mm with visibility requirement of only two seconds. The results show the metro drivers fixating on all of the markers for more than two seconds and those being visible significantly earlier. This shows an important difference between conventional mainline railways and DOO systems where it is necessary to provide drivers with increased flexibility of stopping positions. Moreover, when the DOO equipment is used as a stopping position benchmark, 2-second visibility is too small as it does not factor issues of divided attention between the mirrors and the markers.

In absolute values, the TFD for a stopping position indicator is slightly lower at Gateshead Stadium even though the station also has an island platform. The confined nature of the station contributes to more gazes at the platform. It was observed during the tests that the drivers do not use the marker at Gateshead

Stadium as a stopping position. They usually stop further down the platform, with the first set of doors being next to the marker. It was not the case at other locations. With the participants prioritising the mirrors as a stopping aide, the incorrectly positioned stopping marker becomes only a general benchmark and loses its informativeness.

Total fixation duration tends to decrease with loss of informativeness (Afrooz et al., 2014). Drivers’ attention to the platform at Gateshead Stadium can be caused by a passenger access ramp on the right hand side and a retaining wall on a left hand side. These design elements along with a bridge in front and a ticketing area on top create confined physical environment where the same trends as at Heworth apply.

The participants fixate the least on running signals which is unexpected as the

drivers clearly indicated checking the signals on arrival in the questionnaires (Section 6.3.1). This discrepancy indicates that the drivers might have been trying to answer the questionnaire in a way they thought to be correct. Morrel-Samuels (2002) claims that such behaviour is not unique and answer favourable skewness can be a sign of anonymity concerns. However, in a more demanding environment of an operational railway, checking something which is not required can be skipped in order to address more critical tasks.

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The lowest signal TFD is observed at Gateshead stadium. The running signal there is located on the longitudinal point as the mirror. As the drivers get closer to a stopping point, the angle between the signal, the cab and the mirror becomes wider. The concept of such angle is demonstrated in Figure 36, where it is depicted in red. As the angle gets wider, the signal and the mirror move further apart in a driver’s field of view (FOW). Hence saccadic movements become longer and less time can be devoted to fixations. The FOW angle is smaller at Felling than any other station with an island platform and it shows in the highest TFD on a running signal.

The smallest FOW angle can be seen at Heworth where a driver’s cab is on the same side as the mirror and the signal, but it does not result in the highest TFD. It is possible that the total distance of the signal from the stopping position is simply too big at Heworth making this AOI less relevant for the drivers during the stopping procedure. Groeger et al. (2001) showed that mainline train drivers fixate on a signal 8 seconds before reaching it, which means at least 250 m (at 100 km/h). On entering Heworth station (from a curve) drivers are never more than 150 m away from a signal. However, the research in mainline railways only considers between station signals which do not have to compete with the PTI-related tasks. Hence it is possible to assume that signal sighting distance on station approaches, especially in DOO systems, reduces significantly.

It is also important to note that due to relatively low values for TFD on running signals, these results should be taken with caution. The eye-tracker’s low sampling frequency can cause an error of up to 33ms which is more than 15% in case of Gateshead Stadium signal. The results are not supported by statistical tests too. It was also expected for the drivers to fixate more frequently on Pelaw signal due to convergence of 3 lines (including sidings) right before the station thus higher

informativeness of this signal. However, the results report that drivers treat all of the signals similarly in terms of SA building.

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Figure 36. FOW Angle between a signal, a driver and a mirror (in red)

7.4.2 Elements inducing additional stress and workload during arrivals