What is the proper method to test trailer brakes?

The proper method to test trailer brakes involves setting the trailer brake only and shifting to a low gear. This method allows the driver to assess whether the trailer brakes are functioning properly without the influence of the vehicle's momentum. By engaging the trailer brake and using a low gear, the driver can create a controlled environment to check for responsiveness and effectiveness.

Testing trailer brakes in this manner ensures that the driver can safely gauge how the brakes engage and if they work correctly under load, which is crucial for safe towing. It helps prevent any potential issues that may arise during driving, particularly when going downhill or needing to stop quickly. This method also reduces the risk of damaging the trailer or vehicle compared to trying to test the brakes while driving forward or in reverse, which could lead to jerky movements or loss of control.

The other options do not provide a safe or effective way to check trailer brakes and might lead to accidents or improper assessments. For instance, driving forward and reverse rapidly could lead to a lack of control and make it difficult to assess the brakes' performance appropriately. Testing when empty does not provide an accurate representation of how the brakes will perform when the trailer is loaded. Pulling away from the trailer does not allow for any assessment of the brake functionality itself.