When we (the authors) originally developed the bus route assignment model, we included an arc capacity constraint: Flow  1. After giving this further thought, we deleted this constraint as being...

When we (the authors) originally developed the bus route assignment model, we included an arc capacity constraint: Flow
 1. After giving this further thought, we deleted this constraint as being redundant. Why could we do this? Specifically, why can’t one or more of the flows found by Solver be greater than 1? (Hint: Think in terms of flows out of and into the nodes in the network diagram.)