What is the primary function of a dolly in a double trailer setup?

The primary function of a dolly in a double trailer setup is to connect two trailers. A dolly is a wheeled device that acts as an intermediary between the two trailers, allowing them to be towed in a configuration where one trailer is connected to the dolly, which is then connected to the tractor. This setup enables the safe and effective transport of multiple trailers while ensuring that the weight is distributed and the vehicles remain stable during operation. The dolly plays a crucial role in maintaining connectivity and facilitating the movement of the trailers as part of a larger vehicle combination.