January 1977
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48 Reads
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36 Citations
As a bus travels along a route, its trip time between successive bus stops is subject to random fluctuations. If the bus should fall behind schedule because of this, then some excess passengers will have arrived at the bus stops during the late time and it will take the bus longer to load passengers. A bus, therefore, tends to travel slower and falls even further behind schedule. To compensate for this, the usual strategy of control used by bus operators is to provide some slack time in the schedule so that, normally, a bus can gain some time. The bus then operates under a rule that it may not leave a bus stop ahead of schedule, but will leave immediately if it is late. Actually, this control is not completely stable; if a bus falls so far behind schedule that the extra loading time generated by the lateness exceeds the slack time, the bus will still fall progressively further behind schedule.