Usability of Operational systems in Train Traffic Control : Development of Indicators and Metrics for Measuring Satisfaction

Abstract: This study focuses on how to define and measure usability in systems used for operational train traffic control. The study is conducted as a project for the Swedish Transport Administration (Trafikverket); the authority that is in charge of the train traffic in Sweden. The train dispatchers are the ones that control the train traffic. Their job includes much decision-making and problem solving and they need to have complete control in each situation. The systems used for train dispatching therefore need to be designed to comply with human cognitive capabilities and skills, to support the users in their work and also to be well adapted to the work tasks of the dispatchers. It was therefore decided to evaluate the usability of the systems by looking at how well they support the train dispatchers when they carry out their work tasks. The analysis of the evaluation focused on finding indicators of bad usability in the interaction between the user and his/her systems. Such problems can affect the user's cognitive capabilities and result in unnecessary cognitive demands. Such issues can affect their abilities to control the systems and their work situation. An analysis of the social support in their work environment and their use of the systems was also conducted. The analysis showed that the systems used today had indicators of both good and bad usability. The usability issues that were found caused cognitive work environment problems for the users. Problems like tunnel vision, short-term memory load, orientation issues and unnecessary cognitive workload was the most distinct ones. To investigate further the specific systems used for traffic control, an evaluation instrument was developed. The purpose of the instrument is to be used by the authority to evaluate the usability in their operational traffic control systems. The evaluation of the systems' usability will give greater insight and knowledge about how it actually affects the user's work situation and cognitive capabilities. Key words: Human-computer interaction, usability, train traffic control, train dispatcher, cognitive work environment problems, psychosocial work environment, techno stress, evaluation instrument USOT.