# Cognitive Principles for Remote Condition Monitoring Applied to a Rail Pantograph System
## 6 Discussion  
The exercise of conveying pantograph behaviours and status through a structured HMI, and the feedback from experts, has demonstrated the general success of a cognitively-staged approach to RCM decision making. Furthermore, Table 3 presents some specific HMI requirements for additional information and features within the HMI. The outputs (architecture, design and evaluation outputs) also point to more structural and organizational considerations. From a technical and sensing standpoint, for a system like this to function efficiently, it requires a shared database that contains data from both vehicle and OHLE mounted sensors as well as accurate fault and service histories from both sides. In the UK, rolling stock and infrastructure are managed by separate organisations that, until recently, due to delay attribution systems, had been reluctant to openly share data [44]. For this reason, during the analysis stage, instead of recommending a fault type, if possible, it may be useful to all organisations that own assets that are part of the system to recommend whether the fault is caused by the pantograph or the OHLE. This comes with challenges, since it requires a complex set of accountability mechanisms, particularly where multiple train operators may be operating in the same part of the network. Such an issue may be seen as technical, functional or linked to business arrangements, but the impact on usability and the utility of the solution for an end-user cannot be ignored. Furthermore, the theoretical fault detection system discussed in this paper used lateral acceleration of the contact wire as the primary method of detecting whether a pantograph contact strip is worn. In practice, accelerometers mounted to the contact wire would be costly and require significant maintenance. Instead, one of the other wear indicators discussed in Section 2.1 could be used as an alternative. One benefit of the architecture proposed in this paper is that it is agnostic to the underpinning data sets, with new data enhancing or replacing the data streams presented in the prototype HMIs. One area for future work is to understand the transferability of the conceptual architecture to other rail applications. In terms of the HMI, the outcomes of the SME feedback also highlight that a typical \"Red/Amber/Green\" approach, which is often favoured by designers because of its simplicity [15], may obscure important information that is required in the diagnostic process. As noted by [32], the designer's goal should not always be to aim for simplicity and usability,but rather to effectively represent the necessary complexity of the world being represented in the HMI. However, one area where we had significant deviation from expected results was that, in some cases, the stepwise approach was too constricting and, for want of a better expression, slow for users. This was particularly true in the case of urgent issues that required an immediate response on the part of operators. Earlier work in rail alarm decision making [9; 45] has also highlighted these shortcuts, and indeed such shortcuts are hallmarks of expert decision-making [46; 47]. Therefore, future iterations of the HMI should accommodate such shortcuts within the HMI design. The results of the SME input also highlighted the need for channels to communicate with others, either synchronously (through email notifications) or asynchronously (through notes and annotations that can be viewed by other users in the future [10]). This reiterates the wider organizational factors that must be considered in the design of remote condition monitoring systems [35; 36]. After interviewing members of management from organisations relating to the infrastructure and rolling stock sides, it became clear that one cannot assume that a control room operator has an in-depth knowledge of the entire pantograph/OHLE system.