Steve Gray wrote:
It doesn't matter, the principle is the same. I would imagine practicalities might dictate a mixture of the two.
Quite. There has to be a limit to the length of a train. The American hauliers obviously found no difficulty with hitching those pairs in series but anything longer presumably starts to get unwieldy so having more than one train seems the obvious solution. And I agree, there's no question of a ripple effect. 