Vague and Unsourced

This statement, near the end, is vague and unsourced: "Three carriages, including the bar carriage in the centre, is the minimum possible configuration because of the way the sets are articulated."

1. Does this mean three carriages, exclusive of the power cars, or can the power cars be the other two carriages?
2. Why are three carriages, including the bar carriage, needed? "The way the sets are articulated" makes no sense.

Given these problems, the statement should be sourced and clarified—or else deleted (probably the better option).