Let’s try and clear up the turning radius vs turning circle.
The turning radius of a vehicle is the radius of the smallest circular turn that the vehicle is capable of making. The term turning radius is a technical term that has become popular automotive jargon. In the jargon sense, it is commonly used to mean the full diameter of the smallest circle, but in technical usage the turning radius still is used to denote the radius. This difference in meaning has been in play for a long time, and does no harm except to confuse people encountering it for the first time. The less ambiguous term turning circle avoids the mistaken jargon use of the word 'radius'. As an example, Motor Trend refers to a curb-to-curb turning circle of a 2008 Cadillac CTS as 35.5 feet. But the terminology is not yet settled. The AutoChannel.com refers to turning radius of the same car as 35.5 feet. It is often used as a generalized term rather than a numerical figure.
I emailed Acela and asked for clarification. The Acela 6x6 turning radius OR turning circle is 56.4 ft. In other words, you can turn this unit in a circle with a diameter of 56.4 ft.