How should a signal be regarded if imperfectly displayed?

• A. It must be regarded as the most restrictive indication it can give, except when one or more lower lights of a color light signal aspect is dark, treat that dark aspect as red
• B. It should be disregarded
• C. It should be regarded as the least restrictive indication
• D. Ignore

Answer: (A)

When a signal isn’t displayed perfectly, you must treat it as the most restrictive indication it could reasonably be interpreted as. This safety rule prevents assuming a permissive signal when there’s uncertainty. For color-light signals, an important detail is that if one or more lower lights are dark, that dark element is treated as red, increasing the overall restrictiveness of the signal. So the correct interpretation is effectively the strongest indication that could be inferred from the imperfect display, with darkness signaling red for the affected part. That’s why this approach is chosen: it prioritizes safety over assuming a clearer but unconfirmed signal. The other options would either ignore the imperfection or adopt too permissive an interpretation, which isn’t allowed in railway signaling practice.