Final answer:
Observing aids for visibility must be clearly identified, and visibility charts should be regularly updated.
Step-by-step explanation:
Observing aids for visibility must be clearly identified as to whether they are daytime or nighttime aids. For example, during the day, aids such as road signs, traffic lights, and reflective materials on vehicles ensure visibility. On the other hand, during the night, aids such as streetlights, reflective road markings, and headlights provide visibility.
As for visibility charts, they need to be updated regularly to ensure their accuracy. It is recommended to update visibility charts at least once a year. This helps to reflect any changes in the environment, such as new constructions, changes in road conditions, or even changes in weather patterns that could affect visibility.