You must avoid driving next to other vehicles on multi-lane roads because:

Avoiding driving next to other vehicles on multi-lane roads is primarily important because someone may crowd your lane. This situation can arise when a driver does not properly judge their space in relation to your vehicle, potentially leading to a dangerous situation. If you're in the same lane as another vehicle, it can increase the risk of a sideswipe collision, especially if that vehicle attempts to change lanes without sufficient clearance or awareness of your presence.

By maintaining distance from other vehicles, you give yourself more room to safely maneuver and react to unexpected changes in traffic conditions. Being aware of your surroundings and spacing out from other vehicles helps enhance safety and provides you with a better view of the road ahead, allowing for timely responses to any hazards.

Understanding this principle is crucial for defensive driving, as it encourages maintaining a safe buffer zone between vehicles, reducing the likelihood of collisions and ensuring a smoother flow of traffic on multi-lane roads.