What should a driver primarily rely on for safe lane changes?

For safe lane changes, a driver should primarily rely on checking mirrors and the blind spot because this practice ensures that the surrounding environment is clear of obstacles or other vehicles. Checking mirrors provides a view of what’s directly behind and alongside the vehicle, allowing the driver to assess the position and speed of other traffic. The blind spot check is crucial since mirrors do not capture everything, particularly vehicles that may be directly to the side or slightly behind and out of the view of the mirrors. This comprehensive observation is essential to prevent collisions during the lane change maneuver.

Using sound of the engine is not a reliable indicator of traffic conditions. GPS navigation, while useful for route planning and directions, does not provide real-time information about other vehicles' positions in relation to the driver. Relying solely on other drivers’ signals can be misleading, as not all drivers indicate their intentions, and some may signal incorrectly. Therefore, the combination of checking mirrors and the blind spot ensures maximum safety during lane changes.