How Useful are Carboard Mock-Ups: the Use of Different Levels of Simulation Fidelity in Assessing Signallers' Workload

Two techniques were utilised: the Bedford Scale and the NASA TLX. Assessments were made with two levels of fidelity. The first used a busy 15 minute scenario with seven different failure conditions using paper based layouts of the new signalling system. The second used a three dimensional representation of the proposed signal box layout for a busy one hour scenario. A key finding was that the new box could be run by two signallers with acceptable levels of workload, even with minor failures. A number of changes to the layout were proposed based on the experience of an hour's simulation. The methodology showed that a cardboard model can be a useful tool in a participatory approach aiding the assessment of design and mental workload in a format that can be readily understood by all the stakeholders.