The Integrated Workload Scale (IWS): a new self-report tool to assess railway signaller workload.

Network Rail, who own the railway infrastructure in the UK, have been interested in the assessment of mental workload (MWL) of signallers and control staff for some years. A new model of MWL has been proposed within which to develop a suite of new MWL analytical and empirical assessment tools. One of these is the Integrated Workload Scale (IWS), developed and tested for signallers. This paper describes the development of the IWS and its subsequent testing within two full-scale simulator trials with an NX (entry/exit) panel and an Integrated Electrical Control Centre (IECC) system, and then in the field at signal boxes. The IWS has proven to be a valuable measure of individually experienced peaks and troughs in workload over a period of time or within a particular set of scenarios. It is acceptable to signallers and maps well onto assessments of expected workload on the basis of timeline analysis and subject matter expert commentaries.