Understanding Multimodal Displays to Reduce Distraction in Locomotive Engineers

Abstract

Distraction is a common problem in locomotive cabs. The distractions can either be cognitive, visual, or manual. Head-Up Displays can be a way to mitigate those types of distraction. Head-Up Displays can also potentially be easier to use than current ways of communicating information to the engineer (radio communications and paper). Both aspects of Head-Up Displays were evaluated in this dissertations. First, consider cognitive distractions. Preliminary research suggests that the dispatch radio communications may have significant effects on crew workload and performance, the communications themselves becoming a source of cognitive distraction. This is especially problematic during high workload times when the engineer should be paying attention to events on the forward track. Multi-modal displays that use both visual and auditory channels offer the promise of reducing cognitive distraction in high workload scenarios. In an effort to determine whether multi-modal displays could be used to mitigate radio distraction for the locomotive engineer, I developed and evaluated a multi-modal system that consisted of two parts. One part of the system consisted of a Head-Up Display (HUD) that alerted the engineer when a dispatch message arrived by overlaying a yellow message icon on the HUD. The second part of the system consisted of an in-cab display screen that: a) spoke the message to the engineer when the engineer activated a switch (auditory mode) and b) simultaneously displayed the message on the screen as soon as the engineer activated the switch (visual mode). It was hypothesized that the engineers in the HUD condition would delay the reading of the dispatcher'smessage and, as a consequence, would be more likely to glance at the safety-critical events. Eye movements were measured throughout the occurrence of the safety-critical events. Contrary to the above hypothesis, an analysis of the eye tracking measures indicated that the engineers performed more poorly in the HUD-system condition. Specifically, engineers were less likely to glance towards the safety-critical events in the HUD condition than in the radio condition. The engineers also had overall more head-down time in the HUD condition. Second, consider the use of the HUD to reduce visual distraction. The results showed that although the HUD system presented in the current study does not increase the likelihood that an engineer will detect safety-critical targets (likely because of cognitive distraction), it does provide evidence that engineers who are provided with task-relevant symbology on the HUD are less likely to look for that same task-relevant information on their paperwork. These results indicate that a HUD can indeed reduce visual distraction. The engineers perceived the new HUD system as both easy to use and useful for job completion in both cases: when it was used to delay the dispatcher'smessage and when it was used to display information on the next station stop, speed restriction, and milepost. Given these objective and subjective measures, two things were concluded. First, the aspects of the new HUD-system that seemed to increase engineers? distraction in the safety-critical sections when a dispatcher'smessage arrived should be redesigned to modify how and when the engineer uses the HUD to access the information needed for his or her job functions. Second, the features of the HUD-system unrelated to a dispatcher'smessage that decreased visual distraction and were described as useful to the engineer should be kept for consideration in redesign.