Han,

years ago when the offending devices were enabled, I was struck by how the plentiful open time after initial pbs run somehow then evaporated into thin air. Talking with others in the category we all had similar inability to understand what was going on.

Examining individual schedules revealed what later was termed 'trip parking'. The scheduling expert assured us it could not happen. It can and did.

There were a couple of measures instituted subsequent to this practice that addressed the problem. But not completely. Pilots are like squirrels. If you make the bird feeder harder to get at, the squirrels will simply find a different route to the food.