Devon Metro, I fervently hope that you are never in the position of setting / administering revenue collection rules!
It doesn't take a
long queue to cause problems; experience at my local station is that a single problematic transaction can well exceed the
DfT» 's guideline. When there's only one window open, and no ticket machine, anxious glances at the departure screen / watch become commonplace. The other day there was a cheer from the queue when the
PA▸ announced the train was running late!
The DfT's guidelines should be immaterial. In the midst of an economic crisis, can a ToC really afford to give passengers such a negative experience that they will think twice about any future discretionary travel?