Final answer:
The correct option is maintain proper lane discipline.
Visual checks before changing lanes are essential to identify vehicles in the driver's blind spot, maintain proper lane discipline, and to enhance safety for all road users, including preventing unpredictable maneuvers and ensuring pedestrian safety. This is also why traffic signals are crucial at busy intersections.
Step-by-step explanation:
The reason for making visual checks to the left or right before changing lanes is primarily to ensure there are no vehicles in the blind spot. It is critical for the safety of all road users to perform these checks. Blind spots are areas around the vehicle that cannot be directly seen through the mirrors, and so a physical head turn to check is required to cover these areas. Not just other vehicles, but obstacles or pedestrians could potentially be in these blind spots, particularly in urban environments or near crosswalks and intersections.
Beyond the importance of safe lane changes, checking for traffic and pedestrians serves a larger purpose of maintaining proper lane discipline and contributing to traffic predictability, which is essential for road safety. Sudden and unpredictable lane changes can lead to accidents. A car traveling at highway speeds covers significant distance in a short time, making it unsafe to assume that a road is clear without visually confirming.
Instances like the presence of a traffic signal significantly improve pedestrian safety, which is a clear concern at busy intersections. This is also why mechanisms like wires before tollbooths are used, which signal the drivers' approach and help control the flow of traffic.