What action must you take when backing a trailer?

Using a spotter when backing a trailer is essential for safety and effective maneuvering. A spotter serves as an additional set of eyes, helping to ensure that you have a clear view of your environment, especially areas that may be obstructed from your perspective in the driver's seat. This is particularly important when backing up a trailer, as the added length and weight can make it more challenging to navigate tight spaces and avoid obstacles. The spotter can communicate directions, alert you to any hazards, and assist in making precise movements, significantly reducing the risk of accidents.

Looking only in your mirrors is not sufficient because mirrors do not provide a complete field of view, especially in blind spots. Turning to the left when backing may not be practical in every situation, as the direction to turn depends on the layout and the desired path to take. Speeding up to make the turn is also hazardous; backing up should be done slowly and with control to maintain safety and accurately gauge the position of the trailer. These considerations highlight why using a spotter is the most effective and recommended action when backing up a trailer.