How would you handle a signal failure or technical issue while driving?

As a trainee applicant, I would not pretend to know an operational response I have not been trained to carry out. I would explain that my priorities are safety, following the applicable instructions and reporting the concern accurately to the appropriate operational contact. I would stay within my competence and seek clarification rather than guess at a diagnosis or attempt an unauthorised repair. The specific action would depend on the issue, my training and the employer’s procedures.