In mathematics, A and B commute if AB=BA. In commuting, the order does matter. The Town Hall train (that's the one via Town Hall, or is it the one with destination Town Hall?) is not the same as the Museum train (the one to Town Hall, or the one to Museum?)
Changing sides of the world makes a difference, too. Now I'm in Sydney, I no longer need a dog to carry on the escalators. However, I'm having trouble satisfying the request to keep hold of children while boarding the train. At least I am not asked to keep a firm grip on a pram unless it is mine and I am travelling with it.