During nighttime driving, if you approach a slow-moving vehicle ahead signaling right, your best action is to:

The most appropriate action when you approach a slow-moving vehicle ahead that is signaling right is to wait for the signal to be retracted. This is important because the vehicle may be preparing to make a right turn, and overtaking while it is signaling can lead to an accident if the driver turns just as you attempt to pass.

Waiting ensures that you maintain a safe distance and do not engage in risky behavior that could endanger both you and the slow-moving vehicle. It allows for a clear understanding of the intentions of the driver ahead without making sudden maneuvers, which could lead to confusion or collisions.

The other options might encourage hasty decisions that could compromise safety. Moving to the left lane without sufficient visibility or assurance that it is clear can be dangerous. Overtaking without delay may seem like a straightforward option, but doing so in an unclear situation poses significant risks. Flashing headlights can also be misinterpreted and might not be an effective communication method in every situation, especially at night, when visibility is reduced.