Testing whether signals and indicators are clearly visible and recognisable under real operating conditions.
A new signalling concept had been developed based on insights from human perception research. Before it could be introduced into operations, the design needed to be validated to ensure that operators could reliably recognise and interpret the signal in a wide range of environmental conditions.

The validation revealed important limitations in the design under certain conditions. Based on these findings, improvements were proposed to ensure the final signal would meet operational safety requirements.