Which of the following is necessary to do before you switch lanes?

Before switching lanes, it is essential to check your mirrors and blind spot to ensure it is safe to do so. This action helps you become aware of the traffic conditions around you, including any vehicles that may not be visible in your mirrors or those that are approaching quickly from behind. By thoroughly assessing your surroundings, you can avoid potential collisions and make informed decisions while driving.

Using your horn to alert others is not a standard or necessary practice before changing lanes and may even be considered aggressive or unnecessary in many situations. Signaling is crucial when changing lanes, but solely signaling right without checking mirrors and blind spots does not provide you with the full picture of other surrounding vehicles. Speeding up quickly may create a more dangerous situation by reducing the time available for assessing traffic and could result in reckless driving behavior. Therefore, checking mirrors and blind spots is the comprehensive action that promotes safety on the road.