Controllers should avoid crossing points that are not what relative to the runway to be crossed?

The correct answer is that controllers should avoid crossing points that are not perpendicular relative to the runway to be crossed. The rationale behind this is rooted in safety and operational efficiency.

When two runways or taxiways intersect at a perpendicular angle, the likelihood of misunderstandings or visual misidentifications between aircraft is reduced. It allows for clearer communication and better situational awareness for both pilots and controllers, as the paths crossing at a right angle make it easier to see and predict conflict points.

In contrast, when crossing points are not perpendicular—such as parallel or diagonal—there can be increased risk. This is because the crossing aircraft may not be visible to one another, possibly leading to a greater chance of conflict or miscommunication. Additionally, procedural clarity diminishes with non-perpendicular crossing points, making it harder for controllers to manage the safe flow of traffic. Therefore, maintaining perpendicular crossing points is crucial for ensuring the highest level of safety in air traffic operations.